US2406001A

US2406001A - Electrical signaling system

Info

Publication number: US2406001A
Application number: US523626A
Authority: US
Inventors: Deakin Gerald
Original assignee: International Standard Electric Corp
Current assignee: International Standard Electric Corp
Priority date: 1944-02-24
Filing date: 1944-02-24
Publication date: 1946-08-20
Anticipated expiration: 1963-08-20

Description

All@ 209 E4? G. DEAKIN 2940 ELECTRICAL SIGNLING SYSTEM Filed Feb. 24, 1944 5 sheets-sheet 1 vAug.,

394. @.DEAKIN "294 ELECTRICAL SIGNALING SYSTEM Filed F'ebv;Y 24, 1944 .l 5 Sheets-Shes?. 2

' www Aug. Z, i946.

G. DEAKIN i ELECTRICAL SIGNALING SYSTEM Filed Feb'. 24, 1944 -5 Sheets-Sheet 3 T0 [371970019 JELFG'TOI THRU E56/.5 TER H11/05E INVENTOR gefaald AGENT Aug. 2Q, ma. G. DEAKIN ELECTRICAL SIGNALING SYSTEM AGENT Patented ug. 20, i946 ELECTRICAL SIGNALING SYSTEM Gerald Deakin, New York, N. Y., assignor to International Standard Electric Corporation, New York, N. Y., a corporation of Delaware Application February 24, 1944, Serial No. 523,626

28 Claims.

l This invention relates to new and useful improvements in electrical signaling and switching systems and more particularly to improved impulse sending and impulse receiving or registering arrangements for use in telecommunication switching systems such as automatic and semiautomatic telephone exchanges.

An object of the invention is to increase the speed and reliability with which control impulses may be transmitted from a iirst point to a second point, for example, from a sub-station or the like to a control exchange or other position where selecting equipment is located.

With this object in view, I provide an arrangement in which upon the extension of a line to a distant point at which a selective control is to be exercised, a source of alternating current is coupled to the line. A signaling device, such as a dial, is then actuated to periodically reverse the polarity of a uni-directional current conducting device, such as a dry contact rectifier, in the line circuit. At the distant pointy there is connected to the line circuit polarized relay means which responds to the reversals lof polarity of the current ow and controls-switching apparatus thereat.

The pulse cycle of the standard interrupter dial circuit at present used in automatic telephone exchange systems consists of a closure and an opening of a single stepping relay direct current circuit with 4a 60/40 ratio of opening to closure; One digit is recorded per cycle, and the yopening of the circuit is the useful part of the cycle; the closure of the circuit represents time unavoidably wasted to prepare the circuit to receive the next pulse. In alternating current rectier dialing circuits in accordance with my invention the complete pulse cycle consists of two pulses, a positive pulse and a negative pulse each one useful in recording a digit as well as in assisting the restoration of the relay which is operated by the preceding pulse of opposite polarity. For example, in a preferred arrangement in which two oppositely polarized relays are used for responding to the pulses, these two relays operate on a push-up, push-back principle and thus the complete cycle is used by both relays while rectification with polarization places the operation of the two relays 180 out of phase.

The positive and negative pulses consist in fac-t a of trains of positive and negative pulses at the periodicity of the alternating current source, but for all practical purposes these integrated series of pulses act as though they were pulses of the direct current of the proper polarity. In the alternating current impulsing circuits described hereinafter only the back contact of the pulsing relay is used and as it takes very little energy to break the back contact the combination vof two oppositely polarized pulsing relays results in a very high speed dialling circuit.

The stepping relay as at present used in standard systemsfhas to be adjusted (by the tensioning of a spring which is always dinicult and'somewhat unreliable) to Work on both long and short lines. On short lines it becomes heavily magnetized while on long lines it is only partially magnetized. It must fall off quickly on short lines after being heavily magnetized and it must pull up quickly on long lines when weakly magnetized, and it must also fall back quickly on long lines in which appreciable energy may remain stored in the line due to its capacity which tends to retard the release of the stepping relay.

In the dialling system according to my invention, these disadvantages are overcome in a simple and efficient manner. When rectified alternating current is applied to the dialling circuit which is provided with a polarized relay, the relay is pulled up and forced back with equal energy and the effect of the residual energy stored in long lines is neutralized. When a back contact of the kpolarized relay is used for controlling the selective means only a small amount of energy is required to operate the circuit, all of which tends to make the circuit more sensitive and rapid in response.

These and other features and advantages of myl invention will be more clearly understood from the following description of preferred embodiments thereof and the appended claims.

In the accompanying drawings:

Fig. 1 is a block schematic drawing showing sufficient of the layout of an exchange to give a clear understanding of the present invention;

Fig. 2 is a circuit diagram of a subscriber set circuit provided with a rectiiier dial for use in a system in which a direct current loop is present over the line until dialing commences;

Fig. 3 is a Circuit diagram of a modified subscriber set circuit provided with a rectifier dial for use in a system in which alternating current is applied to the line as soon as the register is connected up;

Fig. 4 is a circuit diagram of a register for use with the subscriber set circuit of Fig. 2;

Fig. 5 is a circuit diagram of an alternative arrangement of the pulsing relays in the register;

Fig. 6 is a circuit diagram of a modified register for use with the subscriber set circuit of Fig. 3;

Fig. 7 is a circuit diagram of another modified register for use with the subscriber set circuit of Fig. 2 but employing mechanical digit and change-over switches;

Fig. 8 is a plan view of a rectifier dial showing the finger hole plate and finger stop;

Fig. 9 is an elevation partly in section taken on the line 8-9 of Fig. 8;

Fig. 10 is a section taken on the line III- IIB of Fig. 9;

Fig. l1 is a section taken on the line II-II of Fig. 9, and

Fig. 12 shows a detail of the spring nest in thc rectifier dial.

Referring first to Fig. 2, the subscriber set circuit shown therein is apart from the rectifier dial of the usual type. The rectifier dial which will be described later in connection with Figs. 8 to 12 includes a rotating rectifier R and a home contact spring nest S. The operation of the rectiiie'r dial from a circuit point of View is as follows: When the finger wheel is moved off normal a pin P3 allows spring B to break contact with spring C which removes a short circuit from the rectier R, and to make contact with spring A which short circuits the induction coil and transmitter. Pin PI causes spring F to break `contact with spring G until shortly before the first finger hole reaches the finger stop; in other words, the line circuit is momentarily opened each time the nger wheel is turned to the finger stop. When the finger wheel is released the rectifier R makes one-half of a revolution for each finger hole passing the linger stop but before the last nger hole passes the finger stop PI again opens contact between the springs F and Gr thereby momentarily opening the line circuit which causes the digit change-over in the register to take place. As will be clear from the subsequent description of the rectifier dial, the rectifier is always returned to its predetermined position of polarity. Thus, should an odd digit be dialed the rectiiier is given a half revolution to restore it to its normal position while contact between springs F and G is open.

From what has been said above it will be seen that when the 'digit 1 is dialed the initial closure of the line through the rectifier R in its normal position sends the first pulse to record the digit 1 and that when the finger wheel is released the circuit is opened for the change-over before the rectifier reverses the current.

The sub-station set circuit shown in Fig. 2 is intended for use with a system incorporating registers of the kind shown in Fig. 4, in which a direct current loop is present over the subscribers line until dialing actually commences. In an alternative method of operation alternating current is applied to the subscribers line as soon as the register is connected up. In this case the subscribers set circuit is as illustrated in Fig. 3. In this arrangement the contact springs F and G shown in Fig. 2, have been omitted as it is not necessary to open the line circuit when the rectifier dial is moved off normal.

The construction of a suitable'rectifier dial is lustrated in Figs. 8 to 12 and will now be described. Referring first particularly to Figs. 9 and 10, the dial consists of two main parts, an upper part I housing the home contact nest HC and a lower part 2 housing the rotating recti fier S.

In the upper housing I -is mounted v'a finger wheel 3 provided with the usual finger holes and attached to a shaft '4 which rotates in a sleeve 5 in the housing I when driven by a coiled spring 6, one end of which is attached to the finger wheel 3, while the other rests in a groove in the housing part I. A segment 'I is attached to shaft 4 by nut 8. A pawl 9 is pivoted to the segment I and tends to engage the teeth of a ratchet wheel I9 under the tension of a spring Ia..

Ratchet wheel I0 and a gear wheel II are attached to each other and rotate freely on the lower extension of shaft Il. They are held in position by the flat head IIa of a bearing pin I2 when the lower part 2 housing the rectifier unit is mounted in position. Ratchet wheel II] has a number of teeth corresponding to the number of positions of the finger wheel 3. Every other tooth is relatively long (in a radial sense). When the finger wheel 3 is in its normal position one edge of the segment 'I rests against a back stop I3 formed in the housing I and a. raised surface I4 on the inner periphery of the housing I adjacent the stop I3 lifts the pawl 9 so that it engages only the deep teeth of a ratchet Il).

When the finger wheel 3 is rotated by the user, the segment 'I moves clockwise and when it has moved an angular distance 'equal to'about one finger hole spacing, the raised surface I4 no longer bears on the pawl 9 and the latter rotates slightly about its pivot so as to engage both the long and the short teeth of the ratchet wheel ID. Should the finger wheel be turned a distance equal to five linger holes, -t'hat is, should the digit 3 be dialed, since there is a, space equal to two finger holes between the hole number l and the finger stop I9, the pawl 9 will engage a short tooth. When the finger wheel is released the spring 6 will rotate the ratchet wheel III counterclockwise. As the segment I 'approaches its home position, the pawl Il engages the raised surface I4 and thus disengages the short tooth but reengages the next long tooth just before the segment I comes to rest against the back stop I3. The object of this arrangement is to insure that the rectifier S always returns to its predetermined position of polarity.

The home spring nest consists of five springs A, B, C, F and G, Fig. 10, mounted i-n a block of insulating material 36 fixed to the upper housing I. Two pins PI and P3 are mounted on the segment I in such position that when the nger wlheel is moved ofi normal, pin PI opens the contact lbetween springs F and G, whilst pin P3 opens the contact between springs B and C and permits contact to be made between springs A and B. The segment 'I is of insulating material.

Assume now that the digi-t 1 is dialed. When the finger is placed in hole number "1, Fig. 8, vand the finger wheel is moved ofic normal, pin PI engages the tip I5 of the extension of spring F, Figs. 10 and 12, and Abreaks the normal contact ybetween springs F and G. Spring F is cut away at its lower edge and provided with an inclined lip I6. When the hole number 1 has been moved an angular distance less than two finger hole spaces, pin PI rides over the lip IS, Fig. 12, and disengages the spring F, so that when the finger reaches the finger stop I9 contact between springs F andG is again made. The three home contact springs, A, B and C are shown in their normal positions in Fig. 10. When segment 'I is moved off normal pin P3 disengages spring B thereby causing Ycontact to ybe broken with spring 'C and made with spring A. The springs A, B and C remain inthis .position until the dial returns 'to When the linger wheel 3 is released, after it has moved about three quarters of a finger hole space, pin Pl reengages the projecting lip I6 of spring F and again opens the contact between springs F and G. When segment 'l reaches its normal position against the back stop I3, contact between springs F and G is restored.

The lower part 2 houses the rectiner discs S Figs. 9 and 1l. These are assembled on a bushing 2l of insulating material. Brush Ella is clamped against the rectifier disc on one side of the rectier unit and brush 2th is clamped against the disc on the other side by means of nuts 22. A bearing pin i2 which passes through the bushing 2l has screwed to it a gear wheel 23 and rotates in bushings 2li attached to the upper and lower covers of the rectifier housing 2. pin I2 is grooved so that when it is slipped through the bore of the bushing 2l the rectiiier assembly' S and brushes 2da and 2gb rotate with the bearing pin l2 and the gear wheel 23.

The upper and lower brushes 2da and glib rub against collector rings 2da and 21th mounted on the inside wall of the housing 2 as shown in Fig. The external connections are connected to the collector rings 2da and Zlib. Gear wheels il and 23 are interconnected by pinions 25 which are attached to each other and held in position by a bearing pin 26 mounted in the lower end of the housing portion 2. wheels are assembled so that when the wheel iii is inthe position shown in Fig. the rotating rectifier unit S is in the position shown in Fig, l1. The ratio of the various gears is such that the rectifier unit S makes one complete revolution when the finger wheel 3 moves an angular distance equal to two linger hole spaces.

The setting of brushes 29a and 2Gb, Fig. l1, .is such that when they engage the insulating surfaces 2l. between the collector rings Eta and Zlib as position 2 of the ratchet wheel passes the normal position i on the return journey, the pin Pi engages lip l 6 of the spring F and opens the contact between springs F, and G. Thus the contact between these springs is opened before the brushes 26a and 29h make contact-with the succeeding collector rings.

As speed control of a rectifier dial is not critical it is suicient to weight the brushes 2da and 26h at their ends so that they act both as governor wings as well as collector brushes.

The method of operation of theimproved dialing system as applied to an arrangement in which a direct current loop is present on the subscribers line until dialing commences will now be described with reference to Figs. 1, 2 and 4.

Referring rst to Fig. i, when a calling subscriber removes his receiver a circuit is completed over the switch hook contacts for the line relay in the subscribers line circuit, an R-link starter and Chooser circuit selects an idle R-link, a register finder associated with which connects up an idle register and a B-link finder selects an idle B-link having associated therewith a rst group selector and a second line finder. The calling line is picked up over the second line finder and an idle iirst line finder having access to the calling line. All these operations take place in the manner fully described in my co-pending application Serial No. 521,160, led February 5, 1944, and form no part of the present invention.

The register shown in Fig. 4 is generally similar to the register described in my co-pending application referred to above and only that part of the circuit has been shown which relates to The bearing l The ratchet and gear '6 rectifier dialing since it is believed that this will enable a clear understanding of the present invention without the introduction of unnecessary complication. When the calling line is picked up, relay RAR, RBR and RCR operate as described in the co-pending application referred to and relay HR is energized over a circuit from battery, the outer back contact of relay RIR, front Contact of relay RBR, resistor R3 and the yupper winding of relay HR to ground. Relay RBR locks up and deenergizes relay RAR as described in the co-pending application referred to. Relay HR locks up over both windings in series with the calling line and over its lowermost front contact completes a circuit for the slow release relay RHR. Relay RIR places battery on both windings of relay DR which are differentially disposed, thus relay DR will not operate as long as both of its windings are energized over back contacts of relays PR and PR Relay RHR removes battery from the resistor R3. Dialling tone is applied over transformer TT. The circuit remains in this condition until the subscriber commences to dial.

When the finger wheel of the rectifier dial is moved from its 'home position the pin P3 opens contacts B and C and removes a short circuit from the vdial rectifier R and the line circuit is momentarily opened. Relay HR releases but not the slow release relay RJR. When the line circuit is closed again, this time through the rectifier Rin the subscribers set, current flows in such a direction as to energize polarized relay PR (-1-), Fig. 4. This current flows from the 490 cycle, 50 volt source over a guard lamp GL, back contacts of relay HR and RAR a wire, dial rectifier R at the sub-station, b wire and back contacts of relays RAR and HR. Relay PR (l-) Yopens its y back contact thus opening one winding of relay DR and causing it to operate. Relay DR energizes relay RSR, which closes a circuit for relay RflR. Relay DR completes a holding circuit for relay RHR over a back contact of relay HR. When relay HR closes its back contact, relay DTR j. operates, locks up and removes dialling tone from the subscribers line.

The rst pulse is always a positive pulse. The

next pulse is a negative pulse which follows immediately after the iirst pulse and causes polarized relay PR to open its back contact and relay PR (-l-) to close its back Contact. This reversal takes place so rapidly that the differential relay DR which is very slightly slow releasing does not fall off. Relay DR thus remains in an unbalanced operated condition until pulsing is completed. The second or negative pulse operates polarized relay PR which removes a short circuit from relay CR2 which locks up over its own front contact, resistor R4, and a front contact of relay RiR. The following or third and positive pulse energizes counting relay CRS and so on.

When the series of pulses ceases, the line circuit is again momentarily opened by the pin Pl of the dial just before it comes to rest, as has already been explained in the preceding description of the construction of the dial. Relays PR and PR remain on their back contacts, thus the differential windings of relay DR are again closed in parallel and relay DR falls off and releases R33. Relay RSR deenergizesrelay RiR but before slow release relay RGR breaks its front contacts, a circuit is momentarily closed from battery, outer left back contacts of relay l closed in my co-pending application above referred to may be adapted for rectier dialling using a subscribers set circuit as shown in Fig. 2.

When the register has picked up the calling line relay RAR releases and relay RBR operates as described in the co-pending application referred to, after which the subscriber hears the dialling tone, the primary circuit of which is closed from a front contact of relay RBR, back contact of relay DTR, the primary winding of tone transformer TT and the dialling tone interrupter DTI to battery. Relay HRi operates over a circuit extending from ground, back contact of relay RIR, front contact of RBR and one winding of relay HRI to battery. Relay HRi connects its second winding from ground to the a wire and connects relay HRZ from battery to the b wire. Relays HRI and HRZ operate in series with the calling line and telephone circuit with the rectifier R, Fig. 2, short circuited. Relay HRI operates slow release relay RIR which places battery on the two windings of a diierential relay DR and ground on the armatures of the oppositely polarized relays PR and PR Relay DR does not operate at this time as its windings are diiferentially disposed. The magnet of the rlrst digit switch Di is energized over a circuit from ground, front contacts of relay RIR,

back contacts of relay PR brush A, terminal I of the in-control switch PI, terminal Oi, brush C of switch DI, winding of magnet DI tc b-attery. Magnet DI attracts its armature but this switch is of the well known type which does not advance its brushes until the de-energization of the magnet. The circuit remains in this condition until the subscriber dials the rst digit. The in-control switch PI and digit switch DI operate except as regards the dialling circuit as described in my co-pending application referred to. The digit switches are, however, provided with an extra bank, as shown at C, whilst the in-control switch PI has an additional bank shown at Ai.

When the subscriber starts to dial the rst digit the line circuit is momentarily opened, as described in connection with Fig. 2. This releases relays HRI and HRZ. Relay HRI places alterhating current on the a wire and connects the two polarized relays PR and PR in multiple to the l? wire. Relay HR! closes the circuit of relay DTR which operates and locks up over a iront Contact of relay RI R. The dialling tone is thus removed from the calling line during the remainder of the connection. Relay RIR is a slo-w release relay which controls the release of the register and performs other functions as described in my co-pending application referred to. It does not fall olf during the short time the line circuit is open when the dial is pulled to the finger stop. After the momentary opening of the line the circuit is again closed at this time through the rectifier', as described in connection with Fig. 2. The rst pulse is always a positive pulse and thus relay PR operates. In so doing it deenergizes magnet DI which advances the first digit switch from position to position l. In position l the magnet DI is again energized, this time over the back contact of relay PR and brush .AI of switch PI. The opening of the back contact of relay PR unbalances the differential relay DR which operates and energizes relay RSR. Relay RSR closes an energizing circuit for the magnet of the in-control switch PI but the brushes of this switch are not advanced. Relay RSR retains energized relay RIR and over another front contact energizes relay RliR over a circuit from ground, front contacts of RIR, back contacts of relay HRZ, front contacts of relay RSR, and winding of relay R4R to battery. Relay RR locks up over its front contact and a back contact of relay HR2.

On the rst reversal of currentin the line, relay PR operates and advances switch DI from position l to position 2. Relay PR makes its back contact and again energizes the magnet of switch Dl. This continues until the proper number of impulses have been sent in. During the reversal of current which operates relay PR and PR alternately, relay DRI does not break its front contact, at least long enough to release relay RBR, since the reversals take place almost instantaneously.

At the end of the series of impulses the 1ine oircuit is again opened as described with reference vto Fig. 2 whereupon both relays PR (-i) and PR remain on their baci; contacts and cause the release of the diierential relay DR which releases relay RSR. Relay RSR opens the circuit or the magnet of switch PI which advances from position 1 to position 2. Relay R3R also over a back contact energizes relay HRA over a circuit from ground, front contacts of relay RIR, back contacts of relay HR2, back contacts of relay RSR, front contacts of RGR and one Winding of relay HRI to battery. Relay HRI operates and disconnects the alternating current from the a wire and in place thereof connects its second winding from ground to the a wire and over another changeover contact disconnects the relays PR and PR and in place thereof connects relay HRZ from battery to the b wire. When the dial comes to rest andcloses the line circuit withthe rectier short circuited, relay HR2 operates in series with the calling line and the second winding of relay HRI. Relay HR2 opens the locking circuit of relay RllR and the circuit of the irst winding of relay HRI. Relays HRI and HRZ remain energized in series until the dial is again pulled for the next selection, after which the second digit switch is advanced in the same manner as the digit switch DI. It will be seen that during the 25 to 50 milli-seconds the line circuit is opened at the end of each selection, the following operations take place in the order given: Relay DR releases, relay RBR releases, relay HRI operates. All this can easily take place in the minimum permissible time of 25 milli-seconds. The 1ine circuit need remain closed 15 milli-seconds to cause relay HRZ to break its back Contact and release relay RllR.

Although the invention has been described as applied to a multi-potential selector system of the kind described in my copending application Serial No, 521,160, filed February 5, 1944, it will be appreciated that it is equally applicable to any type of selector system in which the operation of switching apparatus is controlled by trains of electrical pulses.

Moreover while the detailed description specically describes subscriber dialling circuits, the

pulse responding mechanism would be located inv the T-register. The scope of the invention is, therefore, only to be construed as defined in the appended claims and numerous modiiications within the spirit of the invention will be readily apparent to those skilled in the art.

What is claimed is:

l. In an electrical signaling system, a signaling circuit, a uni-directional current conducting element, means for connecting said element in said signaling circuit, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, means responsive to direction of current flow, means for connecting said last mentioned means to said circuit, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit and selective means controllable by said means responsive to direction of current flow.

2. In an electrical signaling system, a signaling circuit, a, uni-directional current conducting element, means for connecting said element in said signaling circuit, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, polarized relay means, means for connecting said polarized relay means to said circuit, means for intermittently reversing the connection of polarity of said unidirectional current conducting element in said circuit and selective means controllable by said polarized relay means.

3. In an electrical signaling system, a signaling circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said signaling circuit at said rst point, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, direction of current responsive means connected to said circuit at said second point, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit and selective means controllable by said direction of current responsive means.

4. In an electrical signaling system, a signaling circuit extending between iirst and second points. a uni-directional current conducting element, means for connecting said element in said signaling circuit at said first point, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, polarized relay means, means for connecting said polarized relay means to said circuit at said second point, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit and selective means controllable by said polarized relay means.

5. In an electrical signaling system, a signaling circuit extending between first and second points, a uni-directional current conducting element, means for connecting said element in said signaling circuit at said first point, a source of alter nating current, means for coupling said source of alternating current to said signaling circuit, a pair of oppositely polarized relays, means for connecting sai-d pair of relays to said circuit at said second point, means `for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit, and selective means controllable by said pair of polarized relays. t Y

6. In an electrical signaling system, a signaling circuit extending between rst and second points, a uni-directional current conducting element, means for Vconnecting said element in said signaling circuit at said rst point, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, a pair of oppositely polarized relays, means for connecting said pair of relays to said circuit at said second point, back contacts for each of said relays, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit, selective means, and circuits for controlling said selective means including said back contacts.

7. In a telecommunication system, an impulsing circuit extending between first and second points, a uni-directional current conducting element, means for connecting said element in said` impulsing circuit at said rst point, a source of alternating current, means for coupling said source of alternating current to said impulsing circuit polarized relay means, means for connecting said polarized relay means to said impulsing circuit at said second point, means for periodically reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit, selective means at said second point and means for actuating said selective means under the control of said polarized relay means.

8. In a telecommunication system, an impulsing circuit extending between first and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said first point, a source of alternating current, means for coupling said source of alternating current to said impulsing circuit, a pair of oppositely polarized relays, means for connecting said pair of relays to said circuit at said second point, back contacts for eacn of said relays, means for periodically reversing the connection of polarity of said uni-directional current conducting element in said impulsm ing circuit, selective means at said second point and circuits for controlling said selective means including said back contacts.

9. An impulsing circuit according to claim 8, wherein said selective means comprises a chain of counting relays, a set of code relays, circuits for said code relays controlled by said counting relays and circuits for successively energizing said counting relays responsive to the alternate opening of said back contacts of said polarized relays.

l0. In a telephone system, a sub-station circuit, a register controller, means for completing an impulsing circuit between said sub-station circuit and said register controller, a signaling device including a uni-directional current conducting element in said sub-station circuit, a source of alternating current, means for coupling said source of alternating current to said impulsing circuit at said register controller, polarized relay means at said register controller, means for connecting said polarized relay means to said impulsing circuit, means included in said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, digit storing means in said register controller and means for actuating said digit storing means under the control of said polarized relay means.

ll. In a telephone system, a sub-station circuit, a register controller, means for completing an impulsing circuit between said sub-station circuit and said 'register controller, a signaling device including a uni-directional current conducting element in said sub-station circuit, a source of alternating current, means for coupling said source of alternating current to said impulsing circuit at said register controller, a pair of oppositely polarized relays, means for connecting said pair of oppositely polarized relays to said impulsing circuit at said register controller, back contacts for each of said relays, means included in said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, digit storing means in said register controller and means for actuating said digit storing means over circuits including said back contacts.

12. In a telecommunication system, an impulsing circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said first point, a source of alternating current, a signaling device at said rst point, means responsive to initial operation of said signaling device for connecting said source of alternating current to said impulsing circuit at said second point, means responsive to further operation of said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, means responsive to direction of current flow, means for connecting said last mentioned means to said impulsing circuit at said seco-ncl point, selective means at said second point and means for actuating said selective means under the control of said means responsive to direction of current flow.

13. In a telecommunication system, :an impulsing circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said rst point, a source of alternating current, a signaling device at said first point, means responsive to initial operation of said signaling device for connecting said source of alternating current to said impulsing circuit at said second point, means responsive to further operation of said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, a pair of oppositely polarized relays, means for connecting said pair of relays to said impulsing circuit at said second point, back contacts for each of said relays, selective means at said second point and circuits for controlling said selective means including said back contacts.

14. In a telephone system, a sub-station circuit, a register controller, means for completing an impulsing circuit between said sub-station circuit and said register controller, a signaling device including a uni-directional current conducting element in said sub-station circuit, a source of alternating current, means responsive to an initial operation of said signaling device for connecting said source of alternating current to said impulsing circuit at said register controller, means responsive to a further operation of said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, a pair of oppositely polarized relays, means for connecting said pair of polarized relays to said impulsing circuit at said register controller, back contacts for each of said relays, digit storing means in said register controller and means for actuating said digit storing means over circuits including said back contacts.

l5. In a telecommunication system, an impulsing circuit comprising tWo conductors extending between first and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said first point, a source of alternating current at said second point, a line relay and polarized relay means at said second point, means for connecting said line relay to said impulsing circuit at said second point, a signaling device at said first point, means responsive to initial operation of said signaling device to open momentarily said impulsing circuit to cause said line relay to connect said source of alternating current to one of said conductors and to connect said polarized relay means to the other of said conductors at said second point, means responsive to further operation of said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number of times, selective means at said second point and means for actuating said selective means under the control of said polarized relay means.

16. In an electrical signaling system, a signaling circuit, a uni-directional current conducting element, means for connecting said element in said signaling circuit, a source of alternating current, meansfor coupling said source of alternating current to said signaling circuit, a pair of relays, means for connecting each of said relays to said signaling circuit over oppositely poled rectier elements, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit and selective means controllable by said relays.

17. In an electrical signaling system, a signaling circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element insaid signaling circuit at said rst point, a source of alternating current, means for coupling said source of alternating current to said signaling circuit, a pair of relays, means for connecting each of said relays to said signaling circuit at said second point over oppositely poled rectiiier elements, means for intermittently reversing the connection of polarity of said uni-directional current conducting element in said circuit and selective means controllable by said relays.

18. In a telephone system, a sub-station circuit, a register controller, means for completing an impulsing circuit between said sub-station circuit and said register controllen'a signaling device including a uni-directional current conducting eement in said sub-station circuit, a source of alternating current, means for coupling said source of alternating current of said impulsing circuit at said register controller responsive to the completion of said impulsing circuit, relay means at said register controller responsive to direction of current ow, means for connecting said relay means to said impulsing circuit, means included in said signaling device for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a variable and predetermined number or" times, digit storing means in said register controller and means for actuating said digit storing means under the control of said relay means.

19. In a telecommunication system, an impulsing circuit extending between iirst and second points, a uni-directional current conducting element, means for connecting said element in said inipulsing circuit at said first point, a source of alternating current, means for coupling said source or" alternating current to said impulsing circuit, a pair of pulsing relays responsive to opposite directions of current flow, means for connecting said relays to said impulsing circuit at said second point, rst and second selective means at said second point, means for periodically reversing the direction of polarityof said uni-directional current conducting element in said impulsing circuit a predetermined and Variable nurnber of times, means for actuating said first selective means under the control of said pair of relays, a differential relay having a pair of windings, means for alternately energizing the said windings under the control of said pair of pulsing relays during the transmission of impulses to hold said difierential relay operated, and means actuated by the relapse of said differential relay on the termination of the transmission of impulses for transferring the control exercised by said pair of pulsing relays from said first selective means to said second selective means.

20. In a telecommunication system, an impulsing circuit extending between iirst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said first point, a source oi alternating current, means for coupling said source of alternating current to said impulsing circuit, a pair of cppositely polarized relays, means for connecting said relays to said impulsing circuit at said second point, back contacts for said relays, first and second selective `mea-ns at said second point, means for periodically reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a predetermined and variable number of times, circuits including said back contacts for controlling the actuation of said first and second selective means, a dierential relay having a pair of windings, means under the control of said back contacts for alternately energizing the windings or' said differential relay during the transmission of impulses to hold said diierential relay operated, and means actuated by the relapse of said differential relay on the termination of the transmission of impulses for transferring the control exercised by said pair of polarized relays from saidh rst selective means to said second selective means.

21. In a telecommunication system, an impulsing circuit extending between first and second points, an impulsing device, means for connecting said impulsing device to said impulsing circuit at said rst point, impulse responding relay means at said second point, means for connecting said impulse responding relay means to said impulsing circuit, first and second selective means at said second point, means for actuating said impulsing device to send a predetermined and variable number of impulses over said impulsing circuit, means for actuating said first and second selective means under the control of said impulse responding relay means, a dierentia-l relay having a pair of windings, means for alternately energizing said windings under the control of said impulse responding relay means during the transmission o impulses to hold said differential relay operated, and means actuated by the relapse of said differential relay on the termination of the transmission of impulses for transferring the control exercised by said impulse responding re- 16 lay means from said rst selective means to said second selective means.

22. A signaling system` according to claim 12 further comprising means for normally shortircuiting said uni-directional current conducting element, means for removing said short-circuit when said signaling device is initially operated and means for momentarily opening said impulsing circuit during the `further operation of said signaling device.

23. In a telecommunication system an impulsing circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said iirst point, a source of alternating current, means for coupling said source of alternating current to said impulsing circuit, a pair of relays responsive to opposite directions of current iiow, means for connecting said relays to said impulsing circuit at said second point, means for periodically reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit, a selector switch at sai@l second point and means for actuating said selector switch under the control of said pair of relays.

24. 1n a telecommunication system, an impulsing circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said rst point, a source of alternating current, means for connecting said source of alternating current to said impulsing circuit, a pair of relays responsive to opposite directions of current flow, means for connecting said relays to said mpulsing circuit at said second point, means for periodically reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit, a selector switch at said second point, a

control magnet for said selector switch, and av circuit for said control magnet directly controlled by contacts actuated by said pair of relays.

25. In a. telecommunication system, an impulsing circuit extending between first and second points, a uni-directional current conducting element, means for connecting said, element in said impulsing circuit at said rst point, a source of alternating current, means for connecting said source of alternating current to said impulsing circuit, a pair of relays responsive to opposite directions of current now, back contacts for each of said relays, means for connecting said relays to said impulsing circuit at said second point, means for periodicahy reversingr the connection of polarity of said uni-directional current conducting element in said impulsing circuit, a selector switch at said second point, a control magnet for said selector switch and circuits for said control magnet extending over said back contacts of said relays.

26. In a telecommunication system an impulsing circuit extending between rst and second points, a uni-directional current conducting element, means for connecting said element in said impulsing circuit at said first point, a source of alternating current, means for connecting said source of alternating current to said impulsing circuit, a pair of oppositely polarized relays, means for connecting said relays to said impulsing circuit at said second point, means for reversing the connection of polarity of said uni-directional current conducting element in said impulsing circuit a predetermined and variable number of times, iirst and second selector switches at said second point, control switch for transferring a control exercised by said polarized relays from said first switch to said second switch, a differential relay having a pair of windings, means for alternately energizing the said windings under the control of said pair of polarized relays during the transmission of impulses, and means actuated by the relapse of said differential relay on the termination of the transmission of impulses to operate said control switch.

27. In a telephone system a line circuit, a register controller, means for completing an impulsing circuit between said line circuit and said register controller, a signaling device including a rectifier in said line circuit, a. source of alternating current, means for coupling said source of alternating current to said line circuit at said register controller, a pair of oppositely polarized relays at said register controller, means for connecting said polarized relays to said line circuit, means in said signaling device for reversing the connection of polarity of said rectifier in said line circuit a variable and predetermined number of times, first and second digit storing switches in said register controller, an in-control switch for transferring the control by said polarized relays from said rst switch to said second switch, a differential relay having a pair of windings, means for alternately energizing the said windings under the control of said polarized relays during the 30 transmission of a train of impulses, means for momentarily opening said line circuit at the end of said train of impulses, and means actuated by the resultant relapse of said differential relay to advance said in-control switch to transfer the control from said iirst digit switch to said second digit switch.

28. In a telecommunication system, an impulsing circuit extending between rst and second points, a rectifier, means for connecting said rectier in said impulsing circuit at said first point, a source of alternating current, means for connecting said source of alternating current to said impulsing circuit at said second point, a pair of relays responsive to opposite directions of current ow, means for connecting said relays to said impulsing circuit at said second point, rst and second selective means at said second point, means for intermittently reversing the connection of polarity of said rectifier in said impulsing circuit a predetermined and variable number of times, circuits including contacts of said pair of relays for actuating said rst and second selective means, means for momentarily opening said line circuit on the termination of a series of rectifier reversals, and means responsive to said opening for transferring the control by said polarized relays from said first selective means to said second selective means.

GERALD DEAKIN.