US3234514A - Electric pulse signalling system having switching means connected to a constant-voltage source - Google Patents

Electric pulse signalling system having switching means connected to a constant-voltage source Download PDF

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US3234514A
US3234514A US858143A US85814359A US3234514A US 3234514 A US3234514 A US 3234514A US 858143 A US858143 A US 858143A US 85814359 A US85814359 A US 85814359A US 3234514 A US3234514 A US 3234514A
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contact
relay
switching means
signalling
voltage level
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US858143A
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Ward Hugh Jennings
Bundy Ernest Mark
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International Standard Electric Corp
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International Standard Electric Corp
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    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04Q—SELECTING
    • H04Q9/00—Arrangements in telecontrol or telemetry systems for selectively calling a substation from a main station, in which substation desired apparatus is selected for applying a control signal thereto or for obtaining measured values therefrom

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  • This invention relates to electrical signalling systems with particular reference to their use in remote control and supervisory systems.
  • a known method of meeting these requirements is to connect a control and a remote station by a pair of conductors; to connect a battery across the conductors in one sense to provide one of the signalling conditions, e.g., apparatus unitidle; to connect the battery across the conductors in the opposite sense to'provide the other signalling condition, e.g., apparatus unit working; and to disconnect the battery from the conductors between successive signals. That is to say three line conditions, which for simplicity may be referred to as positive, negative and zero, arerequired for the transmission of therequisite information.
  • a voice frequency system is introduced between a control and a remote station, either of two known arrangements maybe used.
  • two voice frequency'channels maybe provided, in which case a positive condition is represented by the transmission of signalling toneover the first channel, negative by the transmission of signalling tone over the second channel, and zero by the inoperative tone on both channels simultaneously.
  • only one voice frequency channel may be used, in which case positive may be represented by a shortpulse of signalling tone on the channel, and negative by a long pulse of signalling tone.
  • the second arrangement suffers from the obvious disadvantage that the speed of transmission of information with such a system is inevitably slower than with two channels and that the delay will vary in accordance with the information transmitted. It is an object of the present invention to overcome .this disadvantage without having to provide a second voice-frequency channel, i.e., by using only two signalling conditions.
  • a method of electric signalling between a transmitter and a-receiver which employs two alternative signalling conditions and in which a signal includes an information time period during which either signalling condition may be transmitted in accordance with information which it is desired to transmit and at least a first change in signalling conditions.
  • an electric signal transmitter having change-over switching means capable of performing at least a first change-over during a transmitted signal, and selection switching means operable to select for transmission during a signal either of two alternative signalling conditions before said first change-over and the other signalling condition after said first changeeover.
  • an electrical signal receiver having change-over switching means responsive to a .change from either to the other of two alternative received signalling conditions; two signal repeaters corresponding to the two signalling conditions, and each capable of selection to the exclusion of the other by an operation of the change-over switching means; and energizing means for the repeaters arranged to operate a repeater which has been selected.
  • the invention will now be described with reference to its application to a remote supervisory system, but it will be understood that the use of the signalling method to be described is not restricted to either remote control or remote supervisory systems. Further, although suitable for use over a single voice-frequency channel, the method may be used with any signalling channel which will trans mit at least two signalling conditions. In the following description the signalling channel is described as a doublecurrent duplex earth-return channel. Alternatively, the signalling channel could be part of a radiolink.
  • FIG. 1 shows the circuit arrangements at a control station.
  • FIG. 2 shows circuit arrangements at a-remote station
  • FIGS. 3, 4 are time charts showing the sequence of operations in the circuits of FIGS. 1,2. For convenience, changes in signalling conditions are shownin both charts.
  • the circuits shown in .FIGS. 1 and 2 contain a multivibrator with a third winding and a follower relay .(CY, CX in FIG. 1 and SY, SX in FIG. 2) of the type having a resistance-capacitance network associated therewith.
  • These multivibrators can asusrne two conditions which may conveniently be designated mark and space, and it is a feature of the multivibrators that the time during which a vibrator remains in one of these conditions is adjustable independently of the time during which it remains in the alternative condition, i.e., that the mark and space conditions need not have equal durations. This feature is made use of in the present invention.
  • a control key (FIG. 1) at the control station initiates the operation of the multivibrator SY, SX (FIG. 2.) at the remote station.
  • a uniselector SW steps once and tests an apparatus unit connected to one of its bank contacts. Relays 3 SP, SN may or may not operate according to the state of the apparatus unit tested.
  • Contacts sp3, m2 in conjunction with contact ss4 determine whether positive or negative battery is applied to the point A, i.e., which of two alternative signalling conditions is to be transmitted.
  • the duplex signalling channel identified in FIGS. 1, 2 as line is capable of assuming more than two conditions during signalling.
  • the signalling conditions will be described in terms of the conditions applied to the point A.
  • Contact ss4 is operated by relay SS which, by its contact ssl, controls the stepping of the uniselector SW.
  • the signalling conditions applied to point A are therefore related in time to the stepping of the uniselector SW. Referring to the time charts of FIGS. 3, 4, it will be seen that while the uniselector SW stands on one contact, the signalling condition applied to a point A refers to the uniselector contact previously tested.
  • relay SS is also operated and contact ss4 changes over.
  • relay CR (FIG. 1) responds to this change-over and releases the multivibrator CY, CX which performs one cycle and comes to rest, causing a uniselector CW to step to and dwell on its first contact.
  • contact ss4 changes over in this manner once in each cycle of the multivibrator SY, SX.
  • the multivibrator CY, CX operates once, and the uniselector CW steps once.
  • the signalling conditions applied at point A cause one or other of relays CP, CN to operate, which in turn cause the lighting or extinguishing of supervisory lamps at the control station.
  • each such signal may be divided into three equal time periods.
  • relay SS is operated, which both prepares the uniselector SW to step to its next bank contact and causes the relay contact ss4 to change over.
  • connections and operation of contacts sp3, snZ are such that this change-over always produces a change in the signalling conditions applied to the point A.
  • the relay SS is released, the uniselector SW steps once and contact ss4- changes back. This may or may not produce a change of signalling conditions'at point A depending on the positions taken up by contacts sp-3, sn2.
  • the signalling conditions applied as a result of contact ss4 moving back are maintained for the first two periods of the next signal. These two periods together constitute the information time period of the signal.
  • the multivibrator, CY, CX starts a cycle of operation and the uniselector CW steps 'once, on the changeover ofcontact ss4 at the end of each second time period. As already explained, contact ss4 moves back at the end of each third time period. If, but only if, a change of signalling conditions results, the relay CR will respond and contact crl will change over.
  • the multivibrator CY, CX is adjusted, so that contact 0171 has time to operate before the multivibrator returns to mark. That is to say, the multi vibrator CY, CX. is adjusted to return to mark during the information time period of a received signal.
  • contact x1 closes causing either relay CP or CN to operate dependand a further cycle of the multivibrator CY, CX is' initiated.
  • the system comprises a transmitter (FIG. 2)and a receiver (FIG. 1), in which three signalling conditions are transmitted and received without requiring three signals of different amplitudes to indicate the three signalling conditions.
  • the transmitter generates a transmission signal including at least one information time period (for instance, time intervals 6, 7, and 8 or time intervals 9, 10, and 11, FIGS. 3 and 4) having at least one information signal portion and another information signal portion in sequence.
  • the transmitter includes a source of voltage having two output terminals, one of the output terminals providing a first voltage level, such as volts associated with contact .9112 of relay SN and with contact SP3 of relay SP, and the other of the output terminals providing a second voltage level distinct from the first voltage level, such as +80 volts associated with contact .9112 of relay SN and with contact sp3 of relay SP.
  • the transmitter further comprises a first switching means including relay multivibrators SY, SX and their associated contacts and relay SS and its contact ss4.
  • the cyclic operation of relay multivibrator SY, SX activates and 'deactivates relay SS to cause contact ss4 to apply a -80 voltage to point A in its unoperated condition through contact sp3 and a +80 voltage to point A in its operated condition through contact m2.
  • the first switching means is selectively coupled to the two output terminals of the voltage source to produce at the output (point A) of the first switching means at least a first change between the first voltage level and the second voltage level as the one information signal portion, this change between the two voltage levels being accomplished upon activation of relay SS by relay multivibrator SY, SX.
  • the transmitter includes a second switching mean-s composed of relay SP and its contact sp3, relay SN and its contact m2, and stepping relay SW and the testing contacts associated therewith.
  • the second switching means is selectively coupled to the two output terminals of the source of voltage by stepping relaySW.
  • the presence of an open or closed supervisory contact (SUP) selects one of the first and second voltage levels for coupling through contact ss4 to point A, the output of the first switching means as another information signal portion.
  • SUP supervisory contact
  • relay multivibrator SY, SX will be activated to place contacts syl and sxl in the S condition to activate relay SS causing contact ss4 to move from contact sp3 to $112 and, hence from 80 volts to a +80 volts.
  • This operation provides in the one information signal portion a changeover between -80 volts to +80 volts.
  • Stepping relay SW will next test contact 3 and if it is assumed that the supervisory contact SUPS is closed, relay SP and relay SN will be operated causing contacts M2 and sp3 to assume their alternate positions so that when relay SS is de activated by the reversal of the operating condition of multivibrator SY, SX, contact ss4 will be returned to its normal indicated position. However, since relays SP and SN have been activated, contact ss4 will be coupled through sp3 to +80 volts whichwill maintain +80 volts at the output of the first switching means (point A).
  • Relay multivibrator SY SX will be activated to its S condition to activate relay SS, thereby causing contact ss4 to move from the illustrated position to its alternate position thereby changing from a 80 volts to a +80 volts due to contacts sp3 and m2 being in their illustrated position.
  • relay SS Upon the re.- turn of relay multivibrator SY, SX to its normal illustrated M condition, relay SS will be deenergized and contact ss4 will return to its normalindicated position, thereby causing a second changeover, but this time from +80 volts to 80 volts. This second changeover represents a third information portion of the information time period.
  • Relays SP and SN will remain in their unenergized condition in this information time periodsince-the steppingrelay SW has landed-on a contactwhosesupervisory switch is inthe open condition and therebyprevents the energization of relays SN andSP and, thus, the another information signalaportion is selected as 80 volts.
  • the information timev period of the transmission signal at point A is transmitted through a transmission medium indicated as LINE and .is presented to the receiver of FIG. 1 which includes therein a third switching means coupled to the transmission medium (LINE), including relayCR and its contact crl.
  • This'third.switchingmeans is responsive to the first change of the one information signal portion and the-selected one of the first voltage level and second voltage level of another information signal portion of the transmission signal for operation thereof.
  • the receiver in accordance with this invention further includes two means, relay CP and its contact and relay CN and its contact, each one of which represents one of the voltage'levels.
  • relay CP represents the 80 voltage level
  • relay CN represents the +80 voltage level.
  • These two means are coupled to the third switching means through contact 011 of the third switching means for exclusive selection of one of the two means by the third switching means during the operationthereof.
  • the energizing means coupled to the third switching means through contact cr1 includes the inhibit winding of relay multivibratorCX, CY and their associated contacts cxl and cyl.
  • the first change in the transmission signal from 80 volts to +80 volts will cause activation of relay CR and movement of .its contact crl from the M to the S position, causing the relay multivibrator to be energized and to move its associated contacts from the M position to the S position to thereby deactivate the'inhibit'winding for a predetermined period.
  • relay multivibrator CX CY will return to its M condition thereby applying through contact 0x1 and the inhibit winding the activating voltage to contact crl.
  • relay SR will remain energized and will hold contact er]; in its S condition, thereby activating relay CN.
  • relay CN is exclusively selected bythe third switching means to indicate the presence of +80 volts in the another information portion.
  • relay CR Since during time intervals 7 and 8 the voltage levels being sent from the transmitter to the receiver is a -80 volts, relay CR will remain unenergized, contact cr1 will remain in its M condition and, hence, relay CP will remain selected or activated to indicate the presence of 80 volts in the another information portion, this selection being exclusively controlled by the third switching means.
  • each signal is divided into three equal time periods.
  • the multivibrator SY, SX at the remote station is arranged to have amark-to-space ratio of 221; while the multivibrator CY, CX at the control station, has a ratio of 1:2. These ratios, however,,are used for descriptive purposes only, and in practice any suitable ratios could be used.
  • the signals will be described in connection with: the transmission of supervisory information from a remote station to a control station, thatis to say; with reference to the signalling conditions applied to the-pointA (FIG. 2) for transmission to the control station.
  • the transmission of information is controlled by the operation .of a controlkey at the-control station.
  • the resultingsignalv is transmitted to the'remote station over .a dupleX channel (line) capablecf. transmitting signals in both directions at the same time.
  • the signalling channel connecting the two stations is capable of assuming only two signalling condtiions, as is the case with a voice-frequency telegraphsignalling channel, and if only one such channel is provided,.it would be necessary to provide directional switching equipment at each end ofthe channel so. that the channel could be workedlfirst in an outward direction for transmitting the control signal and then in an inward-direction for transmitting the signals conveying the supervisory information.
  • Such directional switching equipment is well known in the artand will not be described here.
  • the apparatus at the remote station includes a freerunning multivibrator SY, SX arranged to start. inresponse to a suitable starting signal, in this case the throwing of a control key at the control. station. Also providedv is a uniselector SW which steps under the, control, of the multivibrator SY, SX and tests each bank .contact while it dwells thereon.
  • the condition of each bank contact is determined 'by whether a supervisory contact, connected thereto and indicative of the state of an apparatus unit to be supervised, is open or closed, e.g.,.the condition of bank contact 3 isdetermined by. the open .or closed condition of supervisory contact SUP3, which, in turn, is determined by the conditionof an apparatus unit associated therewith.
  • relay SP will be energized fol-lowed by relay SN. .On the other. hand, if the contact SUP3 is open, neither relay will be energized. Relays SP, SN respond to the condition .of each bankcontact inturn andiby means .of their contacts sp3, m2 determine, in conjunction with contact ss4, the signalling conditions appliedto the point.A. While the uniselector SW stands on one bank contact, a signal relating to the precedingbank contact is transmitted.
  • a multivibrator CY, CX' operates on a start-stop basis and .performs one cyclev for each cycle of the multivibrator SY, SX at the remote station.
  • a uniselectorCW steps under the control of the multivibrator CY, CX. While .the uniselector CW is standing on, one bank contact one of the relays.
  • CP, CN is operated depending upon the signalling condition applied to the point A in relation to the corresponding bank. contact of the uniselector SW at the remote station.
  • a red and a green supervisory lamp is. provided at the control station for each apparatus unit supervised at the remote station. In the example, when a supervisory contact is open the corresponding green lamp glows, and when the supervisory contact is closed the corresponding red lamp is lit and the green lamp is extinguished;
  • FIGS. 3, 4 which also serves to illustrate the nature of the signals transmitted.
  • a signal consists of three successive time periods, e.g., 4, 5, 6.
  • the uniselector SW stands on bank contact 2 while the signal relatingto bank contact 1 is transmitted.
  • the signalling conditions applied to the point A FIG. 1
  • contacts sp3 .9212 are such that the resulting operation of contact .954 always causes a change of signalling conditions at point A, which change is used to initiate a cycle of the multivibrator CY, CX at the con-' trol station.
  • contact ss4 is restored. If the next signal to be transmitted is the same as the last, as is the case if both bank contacts 1, 2; when tested are found in the same condition, the restoration of contact SS4 causes a further change in the signalling condition applied to the point A. On the other hand, if the bank contacts were not in the same condition, the restoration of contact ss4 does not cause a change of signalling conditions at point A.
  • Thevtwo essential features of a signal are, firstly, an information time period during which either of two alternative signalling conditions is applied for transmission and, secondly, a change-over in signalling conditions.
  • the direction of the change-over is not important, that is to say it may be either from a first to a second signalling condition, or from the second to the first condition. Neither is it of importance whether the information time period of a signal precedes or follows the change-over provided the circuits of the transmitter and receiver are suitably designed.
  • a signal may contain a second change of signalling conditions, e.g., at the end of thepen' d 6 in the signals 4, 5, 6, in addition to the two essential features mentioned.
  • FIGS. 1, 2, a1l relays with more than one winding are shown in the mark condition, the arrows indicating the direction of flow of marking current in the individual windings.
  • Single-winding relays are shown in the released condition.
  • relay CP When noinf ormation is being transmitted, relay CP is energized and its contactsare in the opposite positions to those shown, while the contacts of other relays are in the positions indicated.
  • each of themultivibrators is held inoperative by an inhibiting current flowing in its third winding. At the control station, this current also energises relay CP. r In FIGS.
  • a shaded area represents a lapse of time during which a piece of equipment, such as a relay, a key ora contact, is in a condition other than that depicted in FIGS. 1, 2.
  • a piece of equipment such as a relay, a key ora contact
  • FIGS. 1, 2 For the purposes of description, it will be assumed that the supervisory contact SUPS' (FIG. 2) has been closed before the commencement of the operations to be described. It will also be assumed that the supervisory contacts connected to the other bank contacts of the uniselector SW arev all open.
  • Remote station.-Relay SR operates to space and remains at space so long as the control key is thrown.
  • Contact srl opens, interrupting the inhibiting current flowing in the third winding of relay SY.
  • the multivibrator consisting of relay SY and its follower relay SX, is released, changing to space and starting to run freely.
  • relay SS With contact sx1 at space, relay SS is energized, closing contact ssl and energizing the drive magnet of the uniselector SW.
  • the uniselector SW does not step, being of the type which steps on the release of the driving magnet.
  • contact ss4 changes over, changing the signalling condition at point A from negative over contact sp3 to positive over contact sn2.
  • Control station.-Relay CR changes to space in response to the change in signalling condition at point A.
  • contact cr1 interrupts the inhibiting current through the third winding of relay CY.
  • Relay CY followed by relay CX, changes to space.
  • the change-over of contact crl also releases relay CP.
  • contact cxl has moved to space.
  • the slow-to-release guard relay CG is energized.
  • the slow release facility enables the relay CG to remain operated during periods when Time period 1 Remote station-This period is initiated when the multivibrator SY, SX returns to mark of its own accord.
  • the opening of contact 'sxl releases relay SS.
  • the opening of contact ssl releases the. drive magnet of the uniselector SW which steps to bank contact 1.
  • the restoration of contact ss4 changes the signalling condition at point A from positive over contact sn2 to negatlve over contact sp3.
  • Control station.-Relay CR changes to mark in response to the change in signalling condition at the point A.
  • Contact crl in moving to mark, prepares 'a circuit for the operation of relay CP.
  • Time period 2 Remote station. The conditions estaiblished during time period 1 are maintained unchanged.
  • Control stati0n The period is initiated when the multivibrator CY, CX returns to mark of its own accord. For ease of description, the return to mark is regarded as takingplace in the middle of the combined period 1-2 However, the return may take place at any convenient time'after relay CR has had time to operate.
  • contact cxl moves to mark. Current then flows over contact cxl at mark, through the third winding of relay CY, over contact crl at mark, contact 0113 and then through relay CP. This current inhibits-the multivibrator, which is therebyheld in the mark condition. The curernt also energizes relay CP.
  • Time period 3 Remote stati0n.-This period is initiated when the multivibrator SY, SX. changes to space of its own accord. As before, relay SS and magnet SW are energized. The closing of contact ss2 tests bank contact 1 on-which the uniselector SW is now standing. Since the supervisory contact connected to this bank contact'is open,
  • relay SP does not operate.
  • the closing of contact ss 3 prepares a hold circuit for relay SN, which however is Time period 4,
  • the restoration of contact ss4 applies to point A a signalling condition dependent. on the position of, contact .rp3, which in turn is determined by whether or not relay SP was operated when bank contact 1 was tested. Since, however, relay SP was not operated, the restoration of contact ss4 changes the signalling condition from positive over contact m2 to negative over contact sp3.
  • Control stalion.-Relay CR changes to mark in response to the change in signalling conditions at point A.
  • contact crl in moving to mark, prepares a circuit for the operation of relay CP.
  • Time period 5 Remote station-The conditions established during time period 4 are maintained unchanged.
  • Control station The period is initiated when the multivibrator CY, CX returns to mark of its own accord. As before, the multivibrator is inhibited and relay CP is energized. The closing of contact cp2 energizes the drive magnet CW over contact cgl operated. Since contact and is not operated, relay CIA. (not shown, but which is connected to bank contact 1 in the same way as relay C3A is connected to bank contact 3) is not energized. Consequently its contact c1a2 (not shown, but which is connected similarly to contact c3a2) is not operated. Hence, the green lamp corresponding to bank contact It continues to glow.
  • Time period 6 Remote station.-This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized. Relay SP does not operate, since it is assumed that the supervisory contact connected to bank contact 2, on which the uniselector SW is now standing, is open. When contact SS4 changes over, the signalling condition at point A is changed from negative over contact spS to positive over contact sn2.
  • Control. station-Relay CR changes to spacein response to the change. in signallingconditionat point A.
  • the change-over of contact crl deenergizes relay CP, and release the multivibrator which moves to space.
  • the opening of contact. cpZ deenergizes the drive magnet of the uniselector CW which steps to bank contact 2.
  • Time period 7 Remote station.This period is initiated when the multivibrator SY, SX returns tomark of its own accord. As before, relay SS is released. The uniselector SW steps to bank contact 3. With the supervisory contact SUP3 assumed closed, positive battery appears on bank contact 3, but this is ineffective at this stage since contact ml is not operated. Since relay SP was not operated when bank contact 2 was tested, the restoration of contact m4 changes the signalling condition at point A from negative over contact sp3 to positive over contact m2.
  • Control station.Relay CR changes to mark in response to the change in signalling conditions at point A. As before, contact crl, in moving to mark, prepares a circuit for the operation of relay CP.
  • Time period 8 Remote station. The conditions established during time period 7 are maintained unchanged.
  • Control station The period is initiated when the multivibrator. CY, CX returns to mark of its own accord. As before, the multivibrator is inhibited and relay CP and the drive magnet CW are energized. The green lamp corresponding to bank contact 2 continues to glow.
  • Time period 9 Remote station. This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized, and thechange-over ofcontact ss i changes the signalling condition at point A from negative over contact spS to positive over contact 5112. With the uniselector SW standing on bank contact 3, the operation of contact ss2 causes relay SP to be energized, since supervisory contact SUP3.
  • the closing of contact spl prepares a hold circuit for relay SP.
  • the closing of contact sp2 prepares an operating circuit for relay SN.
  • the changeover of contact sp3 prepares the connection of positive battery to point A in time period. 19.
  • Time period 10 Remote station.This period is initiated when the multivibrator SY, SX returns to mark of its own accord. As before, relay SS is released. This time, the restoration of contact .rs4 does not cause a change in signalling conditions at point A, since, this time, contact sp3 is operated. With contact sp3 operated and contact s54 restored, positive battery is connected to point A during time periods 10, 11, which together constitute the information time period of the signal relating to bank contact 3. The opening of contact ssl deenergizes the magnet of theuniselector SW which steps to bank contact 4. The restoration of contact SS2 completes a hold circuit for relay SP over its own contact spl operated.
  • relay SN On the restoration of contact ss3, relay SN is energized over contact sp2 operated. The closing of contact snl prepares a hold circuit for relay SN. The change-over of contact m2 ensures a change of signalling conditions at point A when relay SS is next operated and contact ss4 changes over at the beginning of time period 12.
  • Time period 11 Remote station-The conditions established during time period 10 are maintained unchanged.
  • Time period 12 Remote station-This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized. The change-over of contact ss4 changes the signalling condition at point A, this time, from positive over contact sp3 operated to negative over contact snZ operated. With the uniselector SW now standing on bank contact 4, the operation of contact s52 breaks the hold circuit for relay SP over contact spl. The operation of contact ss3 completes a hold circuit for relay SN. The release of relay SP restores contacts spl, sp2, sp3.
  • Control statz'0n In response to the change of signalling conditions at point A, relay CR changes, this time, from space to mark.
  • the change-over of contact crl deenergizes relay CN and releases the multivibrator which moves to space.
  • the opening of contact cn2 deenergizes the drive magnet of the uniselector CW which steps to bank contact 4.
  • Time period 13 Remote statz'0n.This period is initiated when the multivibrator SY, SX returns to mark of its own accord. As before, relay SS is released. This time, the release of contact ss4 does not cause a change of signalling conditions at A, negative battery being applied before the release over contact sn2 (operated since time period 10) and after the release over contact sp3 (restored in time period 12). The opening of contact ssl results in the uniselector SW stepping to bank contact 5. The restoration of contact ssz is ineffective since relay SP was released in time period 12. The restoration of contact ss3 breaks the hold circuit for relay SN which releases.
  • Time period 14 Remote statz'0n. The conditions established during time period 13 are maintained unchanged.
  • Control stazi0n The period is initiated when the rnultivibrator CY, CX returns to mark of its own accord. As before, when contact 0x1 moves to mark, the multivibrator is inhibited and relay CP is energized.
  • Time period 15 onwards Remote stati0n.-Time period 15 is initiated when the multivibrator SY, SX changes to space of its own accord.
  • the change-over of contact ss4 changes the signalling condition at point A from negative over contact sp3 (restored in time period 12) to positive over contact sn2 (restored in time period 13). Thereafter the action continues in the manner already described.
  • the short circuit includes contact c3a1 operated, wiper cwl, contacts cgZ, cp4 both operated, wiper cw2 and resistor R3.
  • Relay C3A releases.
  • the opening of contact c3a1 breaks the circuit by which relay C3A was held operated.
  • the restoration of contact c3a2 extinguishes' the red lamp corresponding to bank contact 3 and lights'the corresponding green lamp. Thereafter the action is as already described.
  • An electric signal system comprising:
  • a transmitter to generate a transmission signal including at least one information time period having at least one information signal portion and another information signal portion in sequence, said transmitter including a source of voltage having two output terminals, one of said output terminals providing a first voltage level and the other of said output terminals providing a second voltage level distinct from said first voltage level,
  • a first switching means selectively coupled to said two output terminals to produce at the output of said first switching means at least a first change between said first voltage level and said second voltage level as said one information signal portion
  • a second switching means selectively coupled to said two output terminals to select one of said first voltage level and said second voltage level for coupling to said output of said first switch- 13* ing means as, said another information signal portion;
  • a transmission medium coupled to said output of said first switching means for propagation of said transmission signal; and a receiver including a third switching means coupled to said transmission medium responsive to said first change of said oneinformation signal portion and said l t d one f id. first voltage level and said in sequence with said one information signal portion second voltage level of said another information including a selected one of said first voltage level signal portion of said transmission signal for andlsaid second voltage level; operation thereof, a switching means coupled to said transmission medium two means each representingv one of said first voltresponsive to saidfirst change of saidv one informaagelevel and said second voltage level coupled 15 tion signalv portion and-said selected one of said first to said third switching means for exclusive sevoltage level and saidsecond voltage level of said l i f oneof id t means by said third another information signal portion of said transmismeans during the operationthereof, and sion signaltfor operation thereof; energizing means coupled to said third switching two means each representing one of said first voltage means to activate the selected one of said two level and
  • sion signal including at least one information time period having at least one information signalportionandanotherainforrnation.
  • signal portion in sequence comprising:
  • energizing means coupled to said switching means to activatetheselected one of said twomeans.
  • a receiver according to claim 5, wherein said transmission signalincludes in said one information signal portion a second change between said first voltagelevel and said second voltage,level;
  • said switching means is responsive to said first change afirst switching means selectively coupled'to said two in said one information signal por iO to initiate output terminals to produce at the output of said p ati n thereof;
  • first switching me-ans at least a first change between Said energizing means includes said first voltage level and said second voltage level a delay device coupled to Said W C iHg m ans i i fo atio i l i activated by said switching means uponthe inia second; switching-means selectively coupled to said tiation of Operatien thereof to pr vide a pretwo output terminals to select one of-said first voltage determined time delay before Said selecifid one level and said second voltagerlevel for coupling to of Said tWO means is activated y Said energizing said output of said first switching means as said 40 j r d another i f ti i 1 i d said switching means responds to said second change atransmission medium coupled to
  • a receiver according to claim 6, wherein A transmitter. according to l i 2 wherein said transmission signal includes in sequence a plurality said first switching means; produces at said output of qm o r time P and said first switching means a third information signal Sald recelver furthe r portion for said information time period in sequence a phirahty indicators F R f g f with said one and said another information signal sald plulahty of 5315 Information tlme penods portions including a second change between said first two s g i States cone volta e level and said second voltage level; and g 0 one o Sal rs v0 tage level i a V t said second voltage level and the other of said said second switching means remain inoperative to set t corresponding to the.
  • An elfjctrlQslgnal system Comprising: driving means coupledto said first switching means and a trans-utter mcludmg Said testing means to control the sequential testing a firstymonostable relay multivibrator activated 1n of said testing means; and msponse to a control slgnail; said first and second switching means cooperate to a coptrol relay (lollpled to sand f multlvlbratpr said first multivrbrator controlling the
  • a source of'voltage having two outputs, eachoutput providing a different voltage level, one of said voltage levels providing a first signalling 15 7 condition and the other of said voltage levels providing a second signalling condition, a second contact controlled by said first test relay to be selectively connected to said outputs of 1 6 a control relay coupled to said multivibrator, said multivibrator controlling the operating condition of said control relay; a testing uniselector;
  • a tran is i dium; d a second contact controlled by said first test relay to a ixth contact nt ll d b s id t l relay to be selectively connected to said outputs of said source be sequentially coupled to said second and third 0f tag contacts to u l t aid tr i i n di a third contact controlled by said second test relay to a transmission signal having a duration equal to be selectively connected to said outputs of said source the energization-deenergization cycle of said conof g trol relay including a first change between said fourth and fifth contacts controlled by said control refi t d second signalling diti upon rlay interconnecting said uniselector and both said gization f id t l l one f id fi t test relays to render said test relays responsive to the andsecond signalling conditions as determined condition of the device tested by said uniselector; by the condition of the device tested by said first
  • a first relay coupled to one of said contacts of said switching means
  • a second monostable relay multivibrator including signalling conditions upon energization of said control relay, one of said first'and second signalling conditions as determined by the-condition of the device tested by said uniselector and the presence or tabsenee of a second change between said first and second signalling conditions as determined by the condition of the tested previouslytested upon deenergization of said control relay.
  • a transmitter according to claim 10 wherein said control signal for activating said multivibrator is received atsaid transmitter from a remote location over said transmission medium.
  • An electric signal receiver comprising:
  • swltehing means having two outputs responsiveto received signals including information in the form of one of two distinct signalling condition and at least one change between said two signalling conditlons to select one of said two outputs in accordance with which of said two signalling conditions is presinhibiting winding coupled to said switching 40 means responsive to said first change of said transmission signal to render said second multi vibrator operative and to select one of said two contacts of said switching means in accordance with which of said first and second signalling conditions is present;
  • contacts of SE11d SW1ECh1I1g means 15 Selected to a contact controlled by said multivibrator in series with gneder one of'sard first and second relays op said inhibiting winding, said contact closing after a a second uniselector including a plurality of consgg g i i g g 'operanilg tune of i t1- tacts coupled to said first and second relays; r 0 es a i i t i-l fl i means coupled to said first and second relays and .Current through smd i' Sald swltch' said second uniselector to step said second unimg means and of first and Second Telays pending upon WhlCh of said outputs is selected;
  • An electric signal transmitter comprising: relays is rendered operative a monostable relay multivibrator activated in response to acontrol signal; (References on following page) References Cited by the Examiner UNITED STATES PATENTS Nyquist 340-170 XR Rasmussen 1718-70 Potts 178-70 Schaefer 340-203 Thomson 340-167 Place 340-172 Taylor et a1 340-226 X Cornu 340-226 Purington 340-167 Neiswinter 340-226 18 Brown 340-348 Tolsom 340-183 X Barber 340-170 Ingham 178-67 Kuehl 340-348 Hawley 340- 226 X Warnock 340-170 Brosh 340-226 X 10 NEIL C. READ, Primary Examiner.

Description

Feb. 8, 1966 H. J. WARD ETAL ELECTRIC PULSE SIGNALLING SYSTEM HAVING SWITCHING MEANS CONNECTED TO A CONSTANT VOLTAGE SOURCE Filed Dec. 8, 1959 4 Sheets-Sheet 1 J l x o S a, Z 8 Ha Mi. l l v 5 g 5 l g; S Q) m g is v v 5l 1' T vwv-lnr S x s Q Q) I) m f{ Y I I U Q a 1 1 u E n 0% g J INVENTORS. U HUGH J. NARC 2 BY ERNEST M EUNOY s i WCM- Q AGENT Feb. 8, 1966 H. J. WARD ETAL 3,234,514
ELECTRIC PULSE SIGNALLING SYSTEM HAVING SWITCHING MEANS CONNECTED TO A CONSTANT VOLTAGE SOURCE Filed Dec. 8, 1959 4 Sheets-Sheet 2 x S S T 5; A a 1 r f S &|- J, 5|-
V2 2 o 93 /0 \D & wi a, Y
INVENTORS.
LINEv HUGH d. wA/Qo BY ERNEST MBU/VOY w wze AGENT Feb. 8, 1966 H. J. WARD ETAL ELECTRIC PULSE SIGNALLING SYSTEM HAVING SWITCHING MEANS CONNECTED TO A CONSTANT VOLTAGE SOURCE Filed Dec. 8, 1959 4 Sheets-Sheet 5 PERU/ON OF FEM OF cigrK/Qo COND/T/O/V OF FEM DUP/NG TRANSM/TTER 7M5 PER/OD NQ 50/ 3 (ASSUMEQ) 7 RELAYS sxsx,ss,sw 77 7- 7 222 333444555 5w sm/vps ON 0 CONTACT FHA) SP A RELAYS/V 5/0 cow/70mm Z 77, V
//v FORM/1 T/O/V SEA/7 o o 2 2 3 3 4 4 RELAT/NG 7'0 co/vmcr 1 F/RST CHANGE SECOND CHANGE /i7// 17/ Inventors Attorney Feb. 8, 1966 H. J. WARD ETAL 3,234,514
ELECTRIC PULSE SIGNALLING SYSTEM HAVING SWITCHING MEANS CONNECTED TO A CONSTANT VOLTAGE SOURCE Filed Dec. 8, 1959 4 Sheets-Sheet 4 lTEM O COND/T/ON OF FEM DUR/NG 0/ 234567 BQ/OI/AZUM/S SIG CO/VDFf 7 FROM AC0 7 j 7 WFORMA 770/V PE C E l ED RELAT/NG 7'0 CONTACT F/RST CHANGE SECOND CHANGE A m/ 7/7 RELAY CR 7/'- 7 7 RELAYS cY, cx 7 RELAY CP 7 7 W RELAY c/v RELAY cc; V/// DR/VE MAGNET CW 7 W 7 7- RELAY CIA 17 Inventors 'H.J.WARD-E. .BU DY A Home y United States Patent O 3,234,514 ELECTRIC PULSE SIGNALLING SYSTEM HAVING SWITCHING NIEANS CONNECTED TO A CON- STANT-VOLTAGE SOURGE Hugh lennings Ward and Ernest Mark Bundy, Aldwych, London, England, assignors to International Standard Electric Corporation, New York, N. Y.
Filed Dec. 8, 1959, Ser. No. 858,143 Claims priority, application Great Britain, Dec. 12, 1958, 40,170/58 12 Claims. (Cl. 340-147) This invention relates to electrical signalling systems with particular reference to their use in remote control and supervisory systems.
In remote control and supervisory systems it is frequently desirable 'to transmit two signals representing, respectively, the idle and the Working conditions of a unit of apparatus. It is common-practice to transmit over one line a succession of such signals, each successive signal referring to a different apparatus unit. In order that the signal relating to a particular apparatus unit may be directed .to the desired apparatus unit in the .case of a remote control system, or to supervisory equipment corresponding thereto in the case of a remote supervisory systern, it .is necessary that each individual signal should be separately identifiable. A common method of identifying these signals is with reference to their numerical position in. a succession of signals, e. g., by arranging that the fourth signal of a succession relates to the fourth'apparatus unit controlled or supervised. A known method of meeting these requirements is to connect a control and a remote station by a pair of conductors; to connect a battery across the conductors in one sense to provide one of the signalling conditions, e.g., apparatus unitidle; to connect the battery across the conductors in the opposite sense to'provide the other signalling condition, e.g., apparatus unit working; and to disconnect the battery from the conductors between successive signals. That is to say three line conditions, which for simplicity may be referred to as positive, negative and zero, arerequired for the transmission of therequisite information.
Difiiculty arises-when the conductors are replaced, in Whole orpart, by a voice frequency telegraph system, as a signalling channel in such a system can generally assume only .two states and one of theseis assumed continuously when'the channel is inoperative. When such a voice frequency system is introduced between a control and a remote station, either of two known arrangements maybe used. Firstly, two voice frequency'channels maybe provided, in which case a positive condition is represented by the transmission of signalling toneover the first channel, negative by the transmission of signalling tone over the second channel, and zero by the inoperative tone on both channels simultaneously. Secondly, only one voice frequency channel may be used, in which case positive may be represented by a shortpulse of signalling tone on the channel, and negative by a long pulse of signalling tone. The second arrangement suffers from the obvious disadvantage that the speed of transmission of information with such a system is inevitably slower than with two channels and that the delay will vary in accordance with the information transmitted. It is an object of the present invention to overcome .this disadvantage without having to provide a second voice-frequency channel, i.e., by using only two signalling conditions.
According to the invention there is provided a method of electric signalling between a transmitter and a-receiver which employs two alternative signalling conditions and in which a signal includes an information time period during which either signalling condition may be transmitted in accordance with information which it is desired to transmit and at least a first change in signalling conditions.
According to the invention there is also provided an electric signal transmitter having change-over switching means capable of performing at least a first change-over during a transmitted signal, and selection switching means operable to select for transmission during a signal either of two alternative signalling conditions before said first change-over and the other signalling condition after said first changeeover.
According to the invention there is further provided an electrical signal receiver having change-over switching means responsive to a .change from either to the other of two alternative received signalling conditions; two signal repeaters corresponding to the two signalling conditions, and each capable of selection to the exclusion of the other by an operation of the change-over switching means; and energizing means for the repeaters arranged to operate a repeater which has been selected.
The invention will now be described with reference to its application to a remote supervisory system, but it will be understood that the use of the signalling method to be described is not restricted to either remote control or remote supervisory systems. Further, although suitable for use over a single voice-frequency channel, the method may be used with any signalling channel which will trans mit at least two signalling conditions. In the following description the signalling channel is described as a doublecurrent duplex earth-return channel. Alternatively, the signalling channel could be part of a radiolink.
Inthe description, reference will be made to the accompanying drawings in which:
FIG. 1 shows the circuit arrangements at a control station.
'FIG. 2 shows circuit arrangements at a-remote station,
FIGS. 3, 4 are time charts showing the sequence of operations in the circuits of FIGS. 1,2. For convenience, changes in signalling conditions are shownin both charts.
The circuits shown in .FIGS. 1 and 2 contain a multivibrator with a third winding and a follower relay .(CY, CX in FIG. 1 and SY, SX in FIG. 2) of the type having a resistance-capacitance network associated therewith. These multivibrators can asusrne two conditions which may conveniently be designated mark and space, and it is a feature of the multivibrators that the time during which a vibrator remains in one of these conditions is adjustable independently of the time during which it remains in the alternative condition, i.e., that the mark and space conditions need not have equal durations. This feature is made use of in the present invention.
OUTLINE OF OPERATION Throwing a control key (FIG. 1) at the control station initiates the operation of the multivibrator SY, SX (FIG. 2.) at the remote station. At each cycle of operation of this multivibrator, a uniselector SW steps once and tests an apparatus unit connected to one of its bank contacts. Relays 3 SP, SN may or may not operate according to the state of the apparatus unit tested. Contacts sp3, m2 in conjunction with contact ss4 determine whether positive or negative battery is applied to the point A, i.e., which of two alternative signalling conditions is to be transmitted. The duplex signalling channel identified in FIGS. 1, 2 as line is capable of assuming more than two conditions during signalling. However, in order to show clearly that the supervisory information is transmitted by the use of only two signalling conditions, the signalling conditions will be described in terms of the conditions applied to the point A. Contact ss4 is operated by relay SS which, by its contact ssl, controls the stepping of the uniselector SW. The signalling conditions applied to point A are therefore related in time to the stepping of the uniselector SW. Referring to the time charts of FIGS. 3, 4, it will be seen that while the uniselector SW stands on one contact, the signalling condition applied to a point A refers to the uniselector contact previously tested.
As soon as the multivibrator SY, SX starts to operate, relay SS is also operated and contact ss4 changes over. At the control station, relay CR (FIG. 1) responds to this change-over and releases the multivibrator CY, CX which performs one cycle and comes to rest, causing a uniselector CW to step to and dwell on its first contact. As already explained, contact ss4 changes over in this manner once in each cycle of the multivibrator SY, SX. At each such change over, the multivibrator CY, CX operates once, and the uniselector CW steps once. Once in each cycle of the multivibrator CY, CX, the signalling conditions applied at point A cause one or other of relays CP, CN to operate, which in turn cause the lighting or extinguishing of supervisory lamps at the control station.
Referring again to FIGS. 3, 4 the supervisory information is transmitted as a succession of signals, each of which refers to one apparatus unit which has been tested. For convenience of description, each such signal may be divided into three equal time periods. At the end of the second period of each signal, relay SS is operated, which both prepares the uniselector SW to step to its next bank contact and causes the relay contact ss4 to change over. The
connections and operation of contacts sp3, snZ are such that this change-over always produces a change in the signalling conditions applied to the point A. At the end of the third time period of a signal, the relay SS is released, the uniselector SW steps once and contact ss4- changes back. This may or may not produce a change of signalling conditions'at point A depending on the positions taken up by contacts sp-3, sn2. The signalling conditions applied as a result of contact ss4 moving back are maintained for the first two periods of the next signal. These two periods together constitute the information time period of the signal. At the control station, the multivibrator, CY, CX starts a cycle of operation and the uniselector CW steps 'once, on the changeover ofcontact ss4 at the end of each second time period. As already explained, contact ss4 moves back at the end of each third time period. If, but only if, a change of signalling conditions results, the relay CR will respond and contact crl will change over. The multivibrator CY, CX is adjusted, so that contact 0171 has time to operate before the multivibrator returns to mark. That is to say, the multi vibrator CY, CX. is adjusted to return to mark during the information time period of a received signal. When the multivibrator CY, CX returns to mark, contact x1 closes causing either relay CP or CN to operate dependand a further cycle of the multivibrator CY, CX is' initiated.
The system comprises a transmitter (FIG. 2)and a receiver (FIG. 1), in which three signalling conditions are transmitted and received without requiring three signals of different amplitudes to indicate the three signalling conditions.
The transmitter generates a transmission signal including at least one information time period (for instance, time intervals 6, 7, and 8 or time intervals 9, 10, and 11, FIGS. 3 and 4) having at least one information signal portion and another information signal portion in sequence. To produce this transmission signal the transmitter includes a source of voltage having two output terminals, one of the output terminals providing a first voltage level, such as volts associated with contact .9112 of relay SN and with contact SP3 of relay SP, and the other of the output terminals providing a second voltage level distinct from the first voltage level, such as +80 volts associated with contact .9112 of relay SN and with contact sp3 of relay SP.
The transmitter further comprises a first switching means including relay multivibrators SY, SX and their associated contacts and relay SS and its contact ss4. The cyclic operation of relay multivibrator SY, SX activates and 'deactivates relay SS to cause contact ss4 to apply a -80 voltage to point A in its unoperated condition through contact sp3 and a +80 voltage to point A in its operated condition through contact m2. Thus, the first switching means is selectively coupled to the two output terminals of the voltage source to produce at the output (point A) of the first switching means at least a first change between the first voltage level and the second voltage level as the one information signal portion, this change between the two voltage levels being accomplished upon activation of relay SS by relay multivibrator SY, SX.
In addition, the transmitter includes a second switching mean-s composed of relay SP and its contact sp3, relay SN and its contact m2, and stepping relay SW and the testing contacts associated therewith. Through contacts sp3 and sn2 the second switching means is selectively coupled to the two output terminals of the source of voltage by stepping relaySW. The presence of an open or closed supervisory contact (SUP) selects one of the first and second voltage levels for coupling through contact ss4 to point A, the output of the first switching means as another information signal portion.
Considering the operation of the transmitter during the time intervals 9, 10, and 11, an information time period, relay multivibrator SY, SX will be activated to place contacts syl and sxl in the S condition to activate relay SS causing contact ss4 to move from contact sp3 to $112 and, hence from 80 volts to a +80 volts. This operation provides in the one information signal portion a changeover between -80 volts to +80 volts. Stepping relay SW will next test contact 3 and if it is assumed that the supervisory contact SUPS is closed, relay SP and relay SN will be operated causing contacts M2 and sp3 to assume their alternate positions so that when relay SS is de activated by the reversal of the operating condition of multivibrator SY, SX, contact ss4 will be returned to its normal indicated position. However, since relays SP and SN have been activated, contact ss4 will be coupled through sp3 to +80 volts whichwill maintain +80 volts at the output of the first switching means (point A).
Considering now time intervals 6, 7, and 8 constituting another information time period. Relay multivibrator SY, SX will be activated to its S condition to activate relay SS, thereby causing contact ss4 to move from the ilustrated position to its alternate position thereby changing from a 80 volts to a +80 volts due to contacts sp3 and m2 being in their illustrated position. Upon the re.- turn of relay multivibrator SY, SX to its normal illustrated M condition, relay SS will be deenergized and contact ss4 will return to its normalindicated position, thereby causing a second changeover, but this time from +80 volts to 80 volts. This second changeover represents a third information portion of the information time period. Relays SP and SN will remain in their unenergized condition in this information time periodsince-the steppingrelay SW has landed-on a contactwhosesupervisory switch is inthe open condition and therebyprevents the energization of relays SN andSP and, thus, the another information signalaportion is selected as 80 volts.
The information timev period of the transmission signal at point A is transmitted through a transmission medium indicated as LINE and .is presented to the receiver of FIG. 1 which includes therein a third switching means coupled to the transmission medium (LINE), including relayCR and its contact crl. This'third.switchingmeans is responsive to the first change of the one information signal portion and the-selected one of the first voltage level and second voltage level of another information signal portion of the transmission signal for operation thereof.
The receiver in accordance with this invention further includes two means, relay CP and its contact and relay CN and its contact, each one of which represents one of the voltage'levels. For instance, relay CP represents the 80 voltage level and relay CN represents the +80 voltage level. These two means are coupled to the third switching means through contact 011 of the third switching means for exclusive selection of one of the two means by the third switching means during the operationthereof. The energizing means coupled to the third switching means through contact cr1 includes the inhibit winding of relay multivibratorCX, CY and their associated contacts cxl and cyl.
Considering now the operation of the receiver during the information time period including time intervals 9, and .11, the first change in the transmission signal from 80 volts to +80 volts will cause activation of relay CR and movement of .its contact crl from the M to the S position, causing the relay multivibrator to be energized and to move its associated contacts from the M position to the S position to thereby deactivate the'inhibit'winding for a predetermined period. After this predetermined period relay multivibrator CX, CY will return to its M condition thereby applying through contact 0x1 and the inhibit winding the activating voltage to contact crl. Due to the fact that the signal being transmitted remains at +80 volts during time intervals 10 and 1-1, relay SR will remain energized and will hold contact er]; in its S condition, thereby activating relay CN. Thus, relay CN is exclusively selected bythe third switching means to indicate the presence of +80 volts in the another information portion.
Considering now the information time period including time intervals 6, 7', and 8. A-first change of'voltage from a 80 volts to a +80 voltswill activate relay CR and move its contact crl from the M position to the S position to activate relay multivibrator CX, CY for its cyclic operation by removing the inhibiting voltage present at contact 0x1 from the inhibit winding. Since a second change from a +80 volts to 80 volts occurs during these time intervals (third information portion) relay CR and relay multivibrator CX, CY will 'be deenergized and will return to its normal position and in effect will energize relay CP through the inhibit winding of relay multivibrator CX, CY and contact 0x1. Since during time intervals 7 and 8 the voltage levels being sent from the transmitter to the receiver is a -80 volts, relay CR will remain unenergized, contact cr1 will remain in its M condition and, hence, relay CP will remain selected or activated to indicate the presence of 80 volts in the another information portion, this selection being exclusively controlled by the third switching means.
6 DETAILED DESCRIPTION In the followingdescription, it will be convenient to consider each signal as divided into three equal time periods. The multivibrator SY, SX at the remote station is arranged to have amark-to-space ratio of 221; while the multivibrator CY, CX at the control station, has a ratio of 1:2. These ratios, however,,are used for descriptive purposes only, and in practice any suitable ratios could be used.
The signals will be described in connection with: the transmission of supervisory information from a remote station to a control station, thatis to say; with reference to the signalling conditions applied to the-pointA (FIG. 2) for transmission to the control station. In the example to be described, the transmission of information is controlled by the operation .of a controlkey at the-control station. When the control key is operated, the resultingsignalv is transmitted to the'remote station over .a dupleX channel (line) capablecf. transmitting signals in both directions at the same time. However, if the signalling channel connecting the two stations is capable of assuming only two signalling condtiions, as is the case with a voice-frequency telegraphsignalling channel, and if only one such channel is provided,.it would be necessary to provide directional switching equipment at each end ofthe channel so. that the channel could be workedlfirst in an outward direction for transmitting the control signal and then in an inward-direction for transmitting the signals conveying the supervisory information. Such directional switching equipment is well known in the artand will not be described here.
The apparatus at the remote station. includes a freerunning multivibrator SY, SX arranged to start. inresponse to a suitable starting signal, in this case the throwing of a control key at the control. station. Also providedv is a uniselector SW which steps under the, control, of the multivibrator SY, SX and tests each bank .contact while it dwells thereon. The condition of each bank contact is determined 'by whether a supervisory contact, connected thereto and indicative of the state of an apparatus unit to be supervised, is open or closed, e.g.,.the condition of bank contact 3 isdetermined by. the open .or closed condition of supervisory contact SUP3, which, in turn, is determined by the conditionof an apparatus unit associated therewith. If the'contact SUP3 is closed when the uniselector SW steps onthebank contact .3, relay SP will be energized fol-lowed by relay SN. .On the other. hand, if the contact SUP3 is open, neither relay will be energized. Relays SP, SN respond to the condition .of each bankcontact inturn andiby means .of their contacts sp3, m2 determine, in conjunction with contact ss4, the signalling conditions appliedto the point.A. While the uniselector SW stands on one bank contact, a signal relating to the precedingbank contact is transmitted.
At the control station, a multivibrator CY, CX' operates on a start-stop basis and .performs one cyclev for each cycle of the multivibrator SY, SX at the remote station. A uniselectorCW steps under the control of the multivibrator CY, CX. While .the uniselector CW is standing on, one bank contact one of the relays. CP, CN is operated depending upon the signalling condition applied to the point A in relation to the corresponding bank. contact of the uniselector SW at the remote station. A red and a green supervisory lamp is. provided at the control station for each apparatus unit supervised at the remote station. In the example, when a supervisory contact is open the corresponding green lamp glows, and when the supervisory contact is closed the corresponding red lamp is lit and the green lamp is extinguished;
The interaction of the two multivibrators and of the relays and uniselectors associated therewith will be more easily understood by referringto the time chart shown in FIGS. 3, 4 which also serves to illustrate the nature of the signals transmitted. For ease of reference, the op- 7 eration of the equipment will be described stage by stage in a series of time periods numbered from upwards. In the example, a signal consists of three successive time periods, e.g., 4, 5, 6. During the period 4, 5, 6 the uniselector SW stands on bank contact 2 while the signal relatingto bank contact 1 is transmitted. During the first two periods 4, of this signal, the signalling conditions applied to the point A (FIG. 2) for transmission to the control station are determined by which of two alternative conditions is extended over contact sp3 when contact ss4 is restored. These periods 4, 5 together constitute an information time period during which the supervisory information 'from bank contact 1' of uniselector SW is transmitted to the control station and during which, e.g.,- at the end of period 4, the multivibrator CY, CX, at the control station returns to mark to operate one or other of relays CP, CN. At the end of period 5, relay SS at the remote station is energized. The connections and operation of contacts sp3 .9212 are such that the resulting operation of contact .954 always causes a change of signalling conditions at point A, which change is used to initiate a cycle of the multivibrator CY, CX at the con-' trol station. At the end of the third period 6, contact ss4 is restored. If the next signal to be transmitted is the same as the last, as is the case if both bank contacts 1, 2; when tested are found in the same condition, the restoration of contact SS4 causes a further change in the signalling condition applied to the point A. On the other hand, if the bank contacts were not in the same condition, the restoration of contact ss4 does not cause a change of signalling conditions at point A. It is to be understood that the division of a signal into equal time periods was made arbitrarily and for ease of description and is not essential. Thevtwo essential features of a signal are, firstly, an information time period during which either of two alternative signalling conditions is applied for transmission and, secondly, a change-over in signalling conditions. The direction of the change-over is not important, that is to say it may be either from a first to a second signalling condition, or from the second to the first condition. Neither is it of importance whether the information time period of a signal precedes or follows the change-over provided the circuits of the transmitter and receiver are suitably designed. In order that the same signalling condition may be applied during the information time period of successive signals, a signalmay contain a second change of signalling conditions, e.g., at the end of thepen' d 6 in the signals 4, 5, 6, in addition to the two essential features mentioned.
In FIGS. 1, 2,,a1l relays with more than one winding are shown in the mark condition, the arrows indicating the direction of flow of marking current in the individual windings. Single-winding relays are shown in the released condition. When noinf ormation is being transmitted, relay CP is energized and its contactsare in the opposite positions to those shown, while the contacts of other relays are in the positions indicated. When no information is being transmitted, each of themultivibrators is held inoperative by an inhibiting current flowing in its third winding. At the control station, this current also energises relay CP. r In FIGS. 3, 4, a shaded area represents a lapse of time during whicha piece of equipment, such as a relay, a key ora contact, is in a condition other than that depicted in FIGS. 1, 2. For the purposes of description, it will be assumed that the supervisory contact SUPS' (FIG. 2) has been closed before the commencement of the operations to be described. It will also be assumed that the supervisory contacts connected to the other bank contacts of the uniselector SW arev all open. f
.To initiatethe transmission of supervisory information, the control key at the control station is thrown, applying negativebattery to line. Thereafter the following operations occur in the time periods indicated,
. 8 the time periods being numbered in accordance with FIGS. 3, 4.
Time period 0 Remote station.-Relay SR operates to space and remains at space so long as the control key is thrown. Contact srl opens, interrupting the inhibiting current flowing in the third winding of relay SY. The multivibrator, consisting of relay SY and its follower relay SX, is released, changing to space and starting to run freely. With contact sx1 at space, relay SS is energized, closing contact ssl and energizing the drive magnet of the uniselector SW. The uniselector SW, however, does not step, being of the type which steps on the release of the driving magnet. When relay SS is energized, contact ss4 changes over, changing the signalling condition at point A from negative over contact sp3 to positive over contact sn2. I
Control station.-Relay CR changes to space in response to the change in signalling condition at point A. In moving from mark to space, contact cr1 interrupts the inhibiting current through the third winding of relay CY. Relay CY, followed by relay CX, changes to space. The change-over of contact crl also releases relay CP. By the time contact cr1 has moved to space and contact cp3 has closed, contact cxl has moved to space. When contact cpl has closed, the slow-to-release guard relay CG is energized. The slow release facility enables the relay CG to remain operated during periods when Time period 1 Remote station-This period is initiated when the multivibrator SY, SX returns to mark of its own accord. The opening of contact 'sxl releases relay SS. The opening of contact ssl releases the. drive magnet of the uniselector SW which steps to bank contact 1. The restoration of contact ss4 changes the signalling condition at point A from positive over contact sn2 to negatlve over contact sp3.
Control station.-Relay CR changes to mark in response to the change in signalling condition at the point A. Contact crl, in moving to mark, prepares 'a circuit for the operation of relay CP.
Time period 2 Remote station.The conditions estaiblished during time period 1 are maintained unchanged.
Control stati0n.The period is initiated when the multivibrator CY, CX returns to mark of its own accord. For ease of description, the return to mark is regarded as takingplace in the middle of the combined period 1-2 However, the return may take place at any convenient time'after relay CR has had time to operate. When the multivibrator returns to mark, contact cxl moves to mark. Current then flows over contact cxl at mark, through the third winding of relay CY, over contact crl at mark, contact 0113 and then through relay CP. This current inhibits-the multivibrator, which is therebyheld in the mark condition. The curernt also energizes relay CP. Contact cpl opens, but relay CG, being slow to release, remains operated until this contact closes again. Withcontact cgl operated, the closing of contact cpl energlzes' the driving magnet of the uniselector CW. The uniselector CW, however, does not step, being of the type which steps on the release of the driving magnet.
Time period 3 Remote stati0n.-This period is initiated when the multivibrator SY, SX. changes to space of its own accord. As before, relay SS and magnet SW are energized. The closing of contact ss2 tests bank contact 1 on-which the uniselector SW is now standing. Since the supervisory contact connected to this bank contact'is open,
relay SP does not operate. The closing of contact ss 3 prepares a hold circuit for relay SN, which however is Time period 4,
Remote station.This period is initiated when the multivibrator SY, SX returns to mark of its own accord- As before, relay SS is released, magnet SW is deenergized, and the uniselector SW steps to bang contact 2. This con tact,.however, is not tested until contact ssZ is closed in time. period 6.
The restoration of contact ss4 applies to point A a signalling condition dependent. on the position of, contact .rp3, which in turn is determined by whether or not relay SP was operated when bank contact 1 was tested. Since, however, relay SP was not operated, the restoration of contact ss4 changes the signalling condition from positive over contact m2 to negative over contact sp3.
Control stalion.-Relay CR changes to mark in response to the change in signalling conditions at point A. As before, contact crl, in moving to mark, prepares a circuit for the operation of relay CP.
Time period 5 Remote station-The conditions established during time period 4 are maintained unchanged.
Control station.The period is initiated when the multivibrator CY, CX returns to mark of its own accord. As before, the multivibrator is inhibited and relay CP is energized. The closing of contact cp2 energizes the drive magnet CW over contact cgl operated. Since contact and is not operated, relay CIA. (not shown, but which is connected to bank contact 1 in the same way as relay C3A is connected to bank contact 3) is not energized. Consequently its contact c1a2 (not shown, but which is connected similarly to contact c3a2) is not operated. Hence, the green lamp corresponding to bank contact It continues to glow.
Time period 6 Remote station.-This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized. Relay SP does not operate, since it is assumed that the supervisory contact connected to bank contact 2, on which the uniselector SW is now standing, is open. When contact SS4 changes over, the signalling condition at point A is changed from negative over contact spS to positive over contact sn2.
Control. station-Relay CR changes to spacein response to the change. in signallingconditionat point A. As before, the change-over of contact crl deenergizes relay CP, and release the multivibrator which moves to space. The opening of contact. cpZ, as previously, deenergizes the drive magnet of the uniselector CW which steps to bank contact 2.
Time period 7 Remote station.This period is initiated when the multivibrator SY, SX returns tomark of its own accord. As before, relay SS is released. The uniselector SW steps to bank contact 3. With the supervisory contact SUP3 assumed closed, positive battery appears on bank contact 3, but this is ineffective at this stage since contact ml is not operated. Since relay SP was not operated when bank contact 2 was tested, the restoration of contact m4 changes the signalling condition at point A from negative over contact sp3 to positive over contact m2.
Control station.Relay CR changes to mark in response to the change in signalling conditions at point A. As before, contact crl, in moving to mark, prepares a circuit for the operation of relay CP.
Time period 8 Remote station.The conditions established during time period 7 are maintained unchanged.
Control station.-The period is initiated when the multivibrator. CY, CX returns to mark of its own accord. As before, the multivibrator is inhibited and relay CP and the drive magnet CW are energized. The green lamp corresponding to bank contact 2 continues to glow.
Time period 9 Remote station.This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized, and thechange-over ofcontact ss i changes the signalling condition at point A from negative over contact spS to positive over contact 5112. With the uniselector SW standing on bank contact 3, the operation of contact ss2 causes relay SP to be energized, since supervisory contact SUP3.
is assumed closed. The closing of contact spl prepares a hold circuit for relay SP. The closing of contact sp2 prepares an operating circuit for relay SN. The changeover of contact sp3 prepares the connection of positive battery to point A in time period. 19.
Control station.As before, relay CP changes to space in response to the change of signalling conditions at the point A. As before, the change-over of contact crl deenergizes relay CP, and releases the multivibrator which moves to space. As before, the drive magnet CW is released. The uniselector CW steps to bank contact 3.
Time period 10 Remote station.This period is initiated when the multivibrator SY, SX returns to mark of its own accord. As before, relay SS is released. This time, the restoration of contact .rs4 does not cause a change in signalling conditions at point A, since, this time, contact sp3 is operated. With contact sp3 operated and contact s54 restored, positive battery is connected to point A during time periods 10, 11, which together constitute the information time period of the signal relating to bank contact 3. The opening of contact ssl deenergizes the magnet of theuniselector SW which steps to bank contact 4. The restoration of contact SS2 completes a hold circuit for relay SP over its own contact spl operated. On the restoration of contact ss3, relay SN is energized over contact sp2 operated. The closing of contact snl prepares a hold circuit for relay SN. The change-over of contact m2 ensures a change of signalling conditions at point A when relay SS is next operated and contact ss4 changes over at the beginning of time period 12.
Control station.-Since there was no change in signalling conditions at point A, the conditions of time period 9 are maintained unchanged. In particular, relay CR and its contact crl remains at space, thereby preparing a circuit for the operation of relay CN instead of relay CP.
Time period 11 Remote station-The conditions established during time period 10 are maintained unchanged.
Control stati0n.-The period is initiated when the multivibrator CY, CX returns to mark of its own accord. As before, when contact cxl returns to mark, the multivibrator is inhibited by current flowing through the third Winding of relay CY. This time, since contact crl is at space, relay CN is operated in series with the third winding of relay CY. The drive magnet CW is energized over contacts cnZ, cgl both operated. With the uniselector CW standing on bank contact 3 and with contacts c114, cgZ both closed, relay C3A is energized in series with resistor R3. Relay C3A locks in series with its own contact c3ali operated and resistor R3. The change-over of contact 05oz extinguishes the green lamp corresponding to bank contact 3 and lights the corresponding red lamp.
Time period 12 Remote station-This period is initiated when the multivibrator SY, SX changes to space of its own accord. As before, relay SS and magnet SW are energized. The change-over of contact ss4 changes the signalling condition at point A, this time, from positive over contact sp3 operated to negative over contact snZ operated. With the uniselector SW now standing on bank contact 4, the operation of contact s52 breaks the hold circuit for relay SP over contact spl. The operation of contact ss3 completes a hold circuit for relay SN. The release of relay SP restores contacts spl, sp2, sp3.
Control statz'0n.In response to the change of signalling conditions at point A, relay CR changes, this time, from space to mark. The change-over of contact crl deenergizes relay CN and releases the multivibrator which moves to space. The opening of contact cn2 deenergizes the drive magnet of the uniselector CW which steps to bank contact 4.
Time period 13 Remote statz'0n.This period is initiated when the multivibrator SY, SX returns to mark of its own accord. As before, relay SS is released. This time, the release of contact ss4 does not cause a change of signalling conditions at A, negative battery being applied before the release over contact sn2 (operated since time period 10) and after the release over contact sp3 (restored in time period 12). The opening of contact ssl results in the uniselector SW stepping to bank contact 5. The restoration of contact ssz is ineffective since relay SP was released in time period 12. The restoration of contact ss3 breaks the hold circuit for relay SN which releases.
Control stati0n.-As there is no change in signalling condition at point A, relay CR is not operated and re mains at mark. The conditions established during time period 12 are maintained unchanged.
Time period 14 Remote statz'0n.The conditions established during time period 13 are maintained unchanged.
Control stazi0n.The period is initiated when the rnultivibrator CY, CX returns to mark of its own accord. As before, when contact 0x1 moves to mark, the multivibrator is inhibited and relay CP is energized.
Time period 15 onwards Remote stati0n.-Time period 15 is initiated when the multivibrator SY, SX changes to space of its own accord. The change-over of contact ss4 changes the signalling condition at point A from negative over contact sp3 (restored in time period 12) to positive over contact sn2 (restored in time period 13). Thereafter the action continues in the manner already described.
Control stati0n.As before, relay CR changes to space in response to the change of signalling conditions at point A. Thereafter the action continues in the manner already described.
Both stati0ns.The action just described is repeated until control key at the control station is restored. When this occurs, relay SR is operated to mark. The movement of contact srl to mark is ineffective at this stage, since wiper swl is not standing on bank contact 0. The multivibrator SY, SX continues to operate and the uniselector SW continuesto step, as do similarly the multivibrator CY, CX and the uniselector CW, until the uniselector SW steps on to bank contact 0. When this occurs, inhibiting current flows over contact sr1 at mark, wiper swl and the third winding of relay SY. The multivibrator SY, SK and the uniselector SW come to rest. At the control station, inhibiting current flows through the third winding of relay CY in series with relay CP (or CN) as already described. The operation of the multivibrator CY, CX is inhibited, but the uniselector CW is one bank contact behind the uniselector SW. However, the continued energization of relay 0? (or CN) holds contact cpl (or cnl) open and relay CG is released. Contact cgl restores and completes a homing circuit for the uniselector CW which includes the drive magnet CW, the make and break contact mb and the third bank of uniselector CW having a common bank contact for all bank contacts of the other banks (CW1 and CW2) except the home contact 0. When wiper cw3 steps on to bank contact 0, the uniselector-CW comes to rest.
Second cycle Now suppose that the supervisory contact SUP3 is opened before the control key is operated for the second time. Under these conditions, when bank contact 3 is tested by the uniselector SW, relay SP will not operate. The signal relating to bank contact 3, will consist of an information time period (time periods 10, 11) in which, this time, negative battery is applied topoint A, together with a change in signalling conditions at the beginning of time period 12. There will also, this time, be a second change in signalling conditions at the beginning of time period 13. At the control station, the relay CN will, this time, not be operated during the information time period of the signal for bank contact 3. Relay CP, however, will be operated in the manner already described. The closing of contact cp4 completes a short circuit for relay C3A. The short circuit includes contact c3a1 operated, wiper cwl, contacts cgZ, cp4 both operated, wiper cw2 and resistor R3. Relay C3A releases. The opening of contact c3a1 breaks the circuit by which relay C3A was held operated. The restoration of contact c3a2 extinguishes' the red lamp corresponding to bank contact 3 and lights'the corresponding green lamp. Thereafter the action is as already described.
While the principles of the invention have been described above in connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a limitation on the scope of the invention.
What we claim is:
1. An electric signal system comprising:
a transmitter to generate a transmission signal including at least one information time period having at least one information signal portion and another information signal portion in sequence, said transmitter including a source of voltage having two output terminals, one of said output terminals providing a first voltage level and the other of said output terminals providing a second voltage level distinct from said first voltage level,
a first switching means selectively coupled to said two output terminals to produce at the output of said first switching means at least a first change between said first voltage level and said second voltage level as said one information signal portion, and
a second switching means selectively coupled to said two output terminals to select one of said first voltage level and said second voltage level for coupling to said output of said first switch- 13* ing means as, said another information signal portion;
a transmission medium coupled to said output of said first switching means for propagation of said transmission signal; and a receiver including a third switching means coupled to said transmission medium responsive to said first change of said oneinformation signal portion and said l t d one f id. first voltage level and said in sequence with said one information signal portion second voltage level of said another information including a selected one of said first voltage level signal portion of said transmission signal for andlsaid second voltage level; operation thereof, a switching means coupled to said transmission medium two means each representingv one of said first voltresponsive to saidfirst change of saidv one informaagelevel and said second voltage level coupled 15 tion signalv portion and-said selected one of said first to said third switching means for exclusive sevoltage level and saidsecond voltage level of said l i f oneof id t means by said third another information signal portion of said transmismeans during the operationthereof, and sion signaltfor operation thereof; energizing means coupled to said third switching two means each representing one of said first voltage means to activate the selected one of said two level and said second voltage level coupled to Said means. 2. An electric signal transmitter togeneratea transmisswitching meanslfor exclusive selection of one of said two meansby said switching means during operation thereof; and
sion signal including at least one information time period having at least one information signalportionandanotherainforrnation. signal portion in sequence comprising:
energizing means coupled to said switching means to activatetheselected one of said twomeans.
a source of voltage having two output terminals, one of said output terminals providing a first; voltage level and the otherof said output terminals providinga second voltage level distinct from saidfirst volt- 6. A receiver according to claim 5, wherein said transmission signalincludes in said one information signal portion a second change between said first voltagelevel and said second voltage,level;
age level; said switching means is responsive to said first change afirst switching means selectively coupled'to said two in said one information signal por iO to initiate output terminals to produce at the output of said p ati n thereof; first switching me-ans at least a first change between Said energizing means includes said first voltage level and said second voltage level a delay device coupled to Said W C iHg m ans i i fo atio i l i activated by said switching means uponthe inia second; switching-means selectively coupled to said tiation of Operatien thereof to pr vide a pretwo output terminals to select one of-said first voltage determined time delay before Said selecifid one level and said second voltagerlevel for coupling to of Said tWO means is activated y Said energizing said output of said first switching means as said 40 j r d another i f ti i 1 i d said switching means responds to said second change atransmission medium coupled to said output. of said durmg aid predetermined time delay to Selfict the first switching means for propagation of saidtrans p p i 0116 f said two means. mission i L 7. A receiver according to claim 6, wherein A transmitter. according to l i 2 wherein said transmission signal includes in sequence a plurality said first switching means; produces at said output of qm o r time P and said first switching means a third information signal Sald recelver furthe r portion for said information time period in sequence a phirahty indicators F R f g f with said one and said another information signal sald plulahty of 5315 Information tlme penods portions including a second change between said first two s g i States cone volta e level and said second voltage level; and g 0 one o Sal rs v0 tage level i a V t said second voltage level and the other of said said second switching means remain inoperative to set t corresponding to the. other offsaid first lect a g l one of Bald s Voltage levfil and, f voltage, level and saidsecond voltage level; and second voltage level as d another lnformatlon a distributor coupled tosaid two means andsaid plusignal portion. 55, rality of indicators controlled by the repetitious oper- 4. A transmitter according to Claim 2, f rth r incl g ation-of-said delay device to sequentially engage each testing means coupled to said second switching means of said indicators, the state of any one of said indifor testing in sequence the condition of each of a gators being; determined by which of said two means plurality of test terminals to operate said second 9 I d 8 the Period of engagement y Said switching means in accordance with the condition of dlsmbutoli the successive test terminals tested; An elfjctrlQslgnal system Comprising: driving means coupledto said first switching means and a trans-utter mcludmg Said testing means to control the sequential testing a firstymonostable relay multivibrator activated 1n of said testing means; and msponse to a control slgnail; said first and second switching means cooperate to a coptrol relay (lollpled to sand f multlvlbratpr said first multivrbrator controlling the operating generate said transmission signal having in sequence condition of Said control gala v l y, a plurahty of sa d information time periods, each of a first u ms 61E ct ,Said F P- time lieriods, including Said one a first contact controlled by said control relay Information slgna-l-portlon Sald first change and the coupled to said first uniselector to successively presence or absence of a second change between said firstvoltage level and said second voltage level as determined by the condition of said test terminal previously tested, and as said second information period one-of said first voltage level and said second testthe condition of a plurality of devices;
first and second test relays;
a source of'voltage having two outputs, eachoutput providing a different voltage level, one of said voltage levels providing a first signalling 15 7 condition and the other of said voltage levels providing a second signalling condition, a second contact controlled by said first test relay to be selectively connected to said outputs of 1 6 a control relay coupled to said multivibrator, said multivibrator controlling the operating condition of said control relay; a testing uniselector;
said source of voltage; a first contact controlled by said control relay coupled a third contact controlled by said second test relay t0 said uniselector t0 successively test the condition to be selectively connected to said outputs of of aplurality 0f (latices; id o r f v lt first and second test relays;
fourth and fifth contacts controlled by said control a source of voltage h g two p each output relay interconnecting said first uniselector and 10 Providing a difiefent l g levfil, one of Said Voltboth s id te t relays t r d r aid t t relays age levels providing a first signalling condition and responsive to the condition of the device tested the other of Said Voltage levels Providing a Second by said first uniselector; signalling condition;
s a tran is i dium; d a second contact controlled by said first test relay to a ixth contact nt ll d b s id t l relay to be selectively connected to said outputs of said source be sequentially coupled to said second and third 0f tag contacts to u l t aid tr i i n di a third contact controlled by said second test relay to a transmission signal having a duration equal to be selectively connected to said outputs of said source the energization-deenergization cycle of said conof g trol relay including a first change between said fourth and fifth contacts controlled by said control refi t d second signalling diti upon rlay interconnecting said uniselector and both said gization f id t l l one f id fi t test relays to render said test relays responsive to the andsecond signalling conditions as determined condition of the device tested by said uniselector; by the condition of the device tested by said first a a smission medium; and i l t d th presence or absence f a a sixth contact controlled by said control relay to he seemd change between said first and second sequentially coupled to said second and third COI1- signalling conditions as determined by the contacts to supply to said transmission medium a transdition of the device previously tested by said first s n Signal having a duration q l to the 6116f uniselector upon deenergization of said control a Il- 'g Cycle of Said Control relay relay; and eluding a first change between said first and second a receiver coupled to said transmission medium including switching means having two contacts responsive to said transmission signal;
a first relay coupled to one of said contacts of said switching means;
a second relay coupled to the other of said contacts of said switching means; 7
a second monostable relay multivibrator including signalling conditions upon energization of said control relay, one of said first'and second signalling conditions as determined by the-condition of the device tested by said uniselector and the presence or tabsenee of a second change between said first and second signalling conditions as determined by the condition of the tested previouslytested upon deenergization of said control relay.
11. A transmitter according to claim 10, wherein said control signal for activating said multivibrator is received atsaid transmitter from a remote location over said transmission medium.
12 An electric signal receiver comprising:
swltehing means having two outputs responsiveto received signals including information in the form of one of two distinct signalling condition and at least one change between said two signalling conditlons to select one of said two outputs in accordance with which of said two signalling conditions is presinhibiting winding coupled to said switching 40 means responsive to said first change of said transmission signal to render said second multi vibrator operative and to select one of said two contacts of said switching means in accordance with which of said first and second signalling conditions is present;
a seventh contact controlled by said second multivibrator in series with said inhibiting winding, said seventh contact closing after a delay determined by the operating time of said second mulout; w tivibrator to establish a connection for an ina first relay coupled to one of said outputs; hibiting current through said inhibiting winding, 21 second relay coupled to the other of said outputssaid switching means and one of said first and a monostable relay multivibrator including an i hibi second relays depending upon which of said ing winding coupled to said Switching means.
contacts of SE11d SW1ECh1I1g means 15 Selected to a contact controlled by said multivibrator in series with gneder one of'sard first and second relays op said inhibiting winding, said contact closing after a a second uniselector including a plurality of consgg g i i g g 'operanilg tune of i t1- tacts coupled to said first and second relays; r 0 es a i i t i-l fl i means coupled to said first and second relays and .Current through smd i' Sald swltch' said second uniselector to step said second unimg means and of first and Second Telays pending upon WhlCh of said outputs is selected;
selector sequentially to each of said plurality of contacts at each interruption of Said inhibiting a uniselector includmg a plurality of contacts coupled to said first and second relays;
current; and a plurality of indicators each coupled to one of said r 'means coupled to said first and Second relays and said 60 plurality of contacts of said second uniselector uniselector to step said uniselector sequentially to operable to one of two states in accordance with each of said plurality of contacts at each interruption whlchof said first and second relays 1s rendered of said inhibiting current caused by said change beoperative. tween said two signalling conditions; and
y f accofdmg to m 8, Wherem f a plurality of indicators each coupled to one of said trol signal is transmltted from said receiver to said transplurality of contacts operable to one of ttwottates nutter Over saldfraflsmlsslon in accordance with which of said first and second 10. An electric signal transmitter comprising: relays is rendered operative a monostable relay multivibrator activated in response to acontrol signal; (References on following page) References Cited by the Examiner UNITED STATES PATENTS Nyquist 340-170 XR Rasmussen 1718-70 Potts 178-70 Schaefer 340-203 Thomson 340-167 Place 340-172 Taylor et a1 340-226 X Cornu 340-226 Purington 340-167 Neiswinter 340-226 18 Brown 340-348 Tolsom 340-183 X Barber 340-170 Ingham 178-67 Kuehl 340-348 Hawley 340- 226 X Warnock 340-170 Brosh 340-226 X 10 NEIL C. READ, Primary Examiner.
EVERETT R. REYNOLDS, IRVING L. SRAG'OW,
Examiners.

Claims (1)

1. AN ELECTRIC SIGNAL SYSTEM COMPRISING: A TRANSMITTER TO GENERATE A TRANSMISSION SIGNAL INCLUDING AT LEAST ONE INFORMATION TIME PERIOD HAVING AT LEAST ONE INFORMATION SIGNAL PORTION AND ANOTER INFORMATION SIGNAL PORTION IN SEQUENCE, SAID TRANSMITTER INCLUDING A SOURCE OF VOLTAGE HAVING TWO OUTPUT TERMINALS, ONE OF SAID OUTPUT TERMINALS PROVIDING A FIRST VOLTAGE LEVEL AND THE OTHER OF SAID OUTPUT TERMINALS PROVIDING A SECOND VOLTAGE LEVEL DISTINCT FROM SAID FIRST VOLTAGE LEVEL, A FIRST SWITCHING MEANS SELECTIVELY COUPLED TO SAID TWO OUTPUT TERMINALS TO PRODUCE AT THE OUTPUT OF SAID FIRST SWITCHING MEANS AT LEAST A FIRST CHANGE BETWEEN SAID FIRST VOLTAGE LEVEL AND SAID SECOND VOLTAGE LEVEL AS SAID ONE INFORMATION SIGNAL PORTION, AND A SECOND SWITCHING MEANS SELECTIVELY COUPLED TO SAID TWO OUTPUT TERMINALS TO SELECT ONE OF SAID FIRST VOLTAGE LEVEL AND SAID SECOND VOLTAGE LEVEL FOR COUPLING TO SAID OUTPUT OF SAID FIRST SWITCHING MEANS AS SAID ANOTHER INFORMATION SIGNAL PORTION; A TRANSMISSION MEDIUM COUPLED TO SAID OUTPUT OF SAID FIRST SWITCHING MEANS FOR PROPAGATION OF SAID TRANSMISSION SIGNAL; AND A RECEIVER, INCLUDING A THIRD SWITCHING MEANS COUPLED TO SAID TRANSMISSION MEDIUM RESPONSIVE TO SAID FIRST CHANGE OF SAID ONE INFORMATION SIGNAL PORTION AND SAID SELECTED ONE OF SAID FIRST VOLTAGE LEVEL AND SAID SECOND VOLTAGE LEVEL OF SAID ANOTHER INFORMATION SIGNAL PORTION OF SAID TRANSMISSION SIGNAL FOR OPERATION THEREOF, TWO MEANS EACH REPRESENTING ONE OF SAID FIRST VOLTAGE LEVEL AND SAID SECOND VOLTAGE LEVEL COUPLED TO SAID THIRD SWITCHING MEANS FOR EXCLUSIVE SELECTION OF ONE OF SAID TWO MEANS BY SAID THIRD MEANS DURING THE OPERATION THEREOF, AND ENERGIZING MEANS COUPLED TO SAID THIRD SWITCHING MEANS TO ACTIVATE THE SELECTED ONE OF SAID TWO MEANS.
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