US2313238A - Multichannel telegraph system - Google Patents

Description

-March 9, 1943. P. HOLCOMB, JR 2,313,238

MULTICHANNEL TELEGRAPH SYSTEM 5 Sheets-Sheet 1 Filed April 13. 1933' INVENTOR P; P. HOLCOMB JR. C3 BY aw -M 2| ATT RNEY March 9, 1943. P. HOLCOMB, JR 2,313,238

MULTICHANNEL TELEGRAPH SYSTEM I Filed April 15, 1955 5 Sheets-Sheet 2 INVENTOR P. HOLCOMB JR.

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AT ORNEY March 9, 1943. P. HOLCOMB. JR

MULTICHANNEL TELEGRAPH SYSTEM Filed April 13, 1933 5 Sheets-Sheet 3 FIG. 3

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MULTICHANNEL TELEGRAPH SYSTEM Filed April 13, 1933 5 Sheets-Sheet 4 PCR EUOEOD 91F 0ZOJ QUE OP 2-0- INVENTOR P. HQLCOMB JR.

March 9, 1943. P. HOLCOMB, JR

MULTICHANNEL TELEGRAPH SYSTEM 5 Sheets-Sheet 5 Filed April 13, 1933 PRR PCR

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INVENTOR P] HOLCOMB JR.

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Patented Mar. 9, 1943 UNITED STATES PATENT OFFICE MULTICHANNEL TELEGRAPH SYSTEM Philo Holcomb, In, New York, N. Y., assignor to The Western Union Telegraph Company, New York, N. Y., a corporation of New York Application April 13, 1933, Serial No. 666,004

107 Claims.

This invention relates to a signalling system and more particularly to the transmission of signals from a variable number of sources to receiving devices corresponding to the respective sources of signals.

The expression a lane of traflic as used in the following description and referred to in the claims refers to the route or medium over which signalling is accomplished. Among other things a lane of traiiic may be comprised of one or more of the following elements: a wire, a cable strand or conductor, a multiplex channel, a side of a duplex or quadruplex, a carrier current channel, a superimposed circuit, or a radio band channel or circuit.

The single line system carrying a single message at a time has the disadvantage that the capacity of the line generally exceeds the capacity of the transmitting operator and as a result the line is not efiiciently utilized. Attempts to share the line between two or more operators have usually resulted in confusion and delay due to the inevitable struggle for possession of the line.

The multiplex system, while providing a means whereby a small number of operators may share a single line, has permanent channel assignments and therefore is wasteful of line time unless all channels are constantly in use.

One of the objects of the present invention is to produce a signalling system having extreme flexibility in which any one or more of a large group of transmitters may transmit simultaneously over a single lane of trafiic to separate receiving devices or printers and in which the lane will be most efiiciently used. This system I have termed a varioplex or expanding channel system.

Another object is to provide a channel signalling system in which the number of channels may be varied at will and in which there is no idle channel time.

A still further object of the invention is the provision of means for dividing a lane of traflic between any desired number of transmitters, any one or more of which may enter on the lane at any time and share it with every other busy transmitter.

The application of the present invention to a single telegraph line or other single lane of traffic may be likened to a multiplex system operating over that lane in which the number of channels may be expanded substantially instantly from a single channel to any required number of channels.

By way of illustration, if it is assumed that ten operators, who may be located in widely separated branch oflices, are assigned to a single lane of traflic, none of which has suiiicient business to occupy the full lane, but the aggregate business of which substantially fills the lane, then in accordance with the present invention, if only one of the operators has business to transmit at any instant, such operator may take complete possession of the lane. If the lane has a capacity of sixty Words per minute, the message of the single busy operator will be transmitted at that rate. If during the period of such transmission another operator becomes busy he may cut in on the lane Without notice to the first operator and share the lane equally with him on the basis of a two channel multiplex system, each transmitter operating at thirty words per minute. If the first operator completes his business before the second operator, he may close his transmitter out of the lane whereupon the second operator will have full possession and his transmitter is automatically speeded up to the full sixty word rate. Similarly if three operators are busy simultaneously they will share the lane equally, each on a twenty word per minute basis and so on up to the limit of the number of transmitters assigned to the particular lane. The rate of transmission of course will vary with the number of busy operators, but each operator is able to occupy a portion of the lane at any time. The number of channels in operation over the lane is therefore continuously shifting, but the lane is always operating at its maximum capacity as long as any operator has business to transmit thereover.

Further objects of the invention are, in a system of the above nature, to provide means for enabling any operator assigned to the lane to enter his transmitter into or close it out of the lane; for enabling this function to be accomplished automatically under the control of any channel operator or channel transmitter; for

properly synchronizing the transmitter and receiving channeling apparatus and for varying the number of channels operating over the lane without interfering with other active channels other than to change the rate of transmission thereover.

A still further object is to provide a direct, permanent and instantly accessible connection between a multitude of stations or transmitting positions associated with one central ofice and a multitude of stations or receiving positions as-i sociated with another central oflice, over a single line or over a single fixed multiplex channel extending between said central offices.

Another object is to enable one of the fixed channels of a multiplex system to be expanded into any required variable number of sub-channels.

Another object is to enable the speed of op-.

eration over each channel of a variable channel system to be automatically adjusted in accordance with the number of working channels.

Still another object is to enable each channel of a variable channel system to be extended from a central receiving station to individualsub-stations or subscribers omces and to enable the transmitted signals to be recorded on printers individual to each transmitter.

Other objects and advantages of the system will appear as the description proceeds.

The invention will be more fully understood by reference to the following detailed description of preferred embodiments thereof shown on the accompanying drawings in which:

Figure 1 is a circuit diagram of a manually controlled expanding channel system showing the invention applied to one of the fixed channels of a multiplex system.

Figure 2 is a similar view of an automatically controlled system; and

Figures 3, 4 and illustrate more detailed circuit arrangements of a complete automatic expanding channel system with extended channels, Figure 3 showing the transmitting equipment in each of a plurality of sub-stations associated with one central ofllce, Figure 4 showing the transmitting channel controlling equipment at one cen tral office, and Figure 5 showing the receiving equipment at the distant central offlce.

Reference will first be had to Figure 1 which shows the transmitting equipment at station A and the receiving equipment at station B of an expanding channel system. It is to be understood, however, that the system may be duplexed with transmitting and receiving equipment at each station.

The transmitting equipment at station A comprises a number of tape transmitters Tl, T2, T3, etc. (three in the present instance although the number is unlimited). Each tape transmitter comprises the marking and spacing bus bars M and S respectively, a group of five contacts numbered to 5 adapted to be set against one or the other of the bus bars in accordance with the perforations in a. tape and a tape stepping magnet SM. The tape transmitter may be of the form shown in patent to G. R. Benjamin, 1,298,440, granted March 25, 1919. The contacts to 5 of each transmitter are connected to the correspondingly numbered segments of rings I0 of start-stop distributors D|, D2, D3, etc. Each distributor has in addition a rest segment R and a sixth pulse se ent B, the latter of which is connected to one terminal of the stepping magnet SM of its associated transmitter, the opposite terminal thereof being grounded. The brushes Bl, B2, B3, etc. are normally held at rest on segments R by individual latches Li, L2, L3, etc. under the control of release magnets Ml, M2, M3, etc.

The segments to 5 of ring ll of each distributor are multipled to one terminal of the windings to 5 of a bank l2 of polar relays. The opposite terminals of these relays are grounded. The tongues of relays |2 operate between marking and spacing contacts and are connected to segments to 5 of one channel, for instance the c channel 0! ring l3 of the multiplex transmitting distributor TD. The solid ring I4 is connected to the apex of the duplexed line L. The distributor TD also has a pair of local rings I5 and IS, the former being provided with a local segment ll connected by a conductor l8 to one terminal of each of the release magnets Ml, M2, M3, etc. The opposite terminals of these magnets are connected to one contact IQ of individually cut-out switches Cl, C2, C3, etc. and the pivoted arm of each switch is joined to segments SI, S2, S3, etc. respectively of a transmitting mixer TM. There is one segment 8|, S2, etc. for each transmitter Tl, T2, etc. assigned to the 0 channel of the distributor TD. A rotarybrush carrier having stop arms individual to each of the segments S|, S2, etc. is provided, one only of the arms indicated by numeral 2| having a pair of brushes Bl mounted thereon. The remaining arms 2| 2|", etc. serve only as stop arms to arrest the brushes on one or another of the segments SI, S2, etc. These arms cooperate with a stop latch 22 con trolled by a magnet 23 having one terminal grounded and the other terminal connected to the solid ring 24 of the transmitting mixer.

The operation of the transmitting apparatus is as follows: Assume switches Cl, C2 and C3 to be closed on their contacts IS with a supply of tape for each of the transmitters Tl, T2 and T3. Also assume brush B4 to be resting on segment S2 with the brush B6 of the multiplex distributor passingonto local segment When this occurs an impulse is sent from the positive ring |6 through brush B6, segment I! and conductor l8 to release magnet M2 and thence by way of switch C2 to segment S2 and through brush B4 and ring 24 to release magnet 23 and to ground. Latches L2 and 22 are released simultaneously, the former permitting the brush B2 to pass over the segments ofthe distributor D2, thereby operating relays |2 in accordance with the combination set up in the tape transmitter T2. The simultaneous escapement of the brush arm 2| permits it to move around to segment S3, being stopped thereon by engagement of the stop arm 2| with the latch 22. As brush B2 of distributor D2 crosses segment 6, a pulse is sent to the tape stepping magnet SM2 of transmitter T2 to step a new combination into the transmitter. The brush B2 comes to rest on segment R against latch L2.

As the brush B5 of the multiplex distributor crosses the segments of the C-channel on the succeeding revolution it transmits the combination stored in relay bank |2 over the line L. Following this transmission, as brush B6 again engages local segment another impulse is sent over conductor l8 through release magnet M3. switch C3 and segment S3 to release magnet 23, releasing the brush B3 of distributor D3 to set up on the relay bank I2 the code combination stored in the contacts of the transmitter T3. Brush Bl of the transmitting mixer is again released coming to rest on segment SI as stop arm 2| engages stop latch 22. On the next revolution of the multiplex distributor the code combination previously set up on the transmitter T3 is transmitted over the line L and the code set up in the transmitter TI is at the same time stored in relay bank l2. This operation continues as long as each transmitter has any material to transmit, the transmitters Tl, T2 and T3, etc. operating in succession.

If now the tape supply of one of the transmitters becomes exhausted, or for any other reason the operator in charge desires to discontinue the transmission from one of the transmitters. for instance transmitter T2, he throws the corresponding switch (C2 in the present instance) .over to its positive contact, applying steady positive battery to segment S2 of the transmitting mixer. Consequently as the brush B4 is released from segment Si at the time of operation of the distributor DI, it does not come to rest on segment S2, but passes directly thereover on to segment S3. This is due to the circuit set up from positive battery at switch C2 through segment 82, brushes B4 and ring 24 to release magnet 23, causing the latch 22 to be withdrawn from the path of the brush arm 2i as the brushes engage segment S2. Consequently the next local pulse transmitted from local segment I! passes through magnet M3, switch C8 and segment S3 to the release magnet 23, enabling a character from the transmitter T3 to be set up on the multiplex distributor and transmitted over the line following the transmission of a character from transmitter Ti. As long as the switch C2 remains on its positive contact transmitters TI and T3 alternately transmit over the line L upon each revolution of the multiplex distributor. If switch C3 is now moved to its positive contact the transmitter T3 will also be cut out, the brush Bl passing directly from segment SI over segments S2 and S3 and back on to segment SI each time a local pulse is supplied from segment [1. Therefore transmitter Tl has full possession of the C-channel sending a character thereover each revolution of the multiplex distributor.

If it is again desired to enter transmitterT2 on the c-channel it is only necessary for the operator to close switch C2 on its contact i9 thus removing the battery from segment S2. On the next escapement of brush Bl from segment SI, it will come to rest on segment S2 and the next local impulse from segment II will be diverted through magnet M2 by way of segment S2 to the release magnet 23 bringing transmitter T2 into operation alternately with transmitter Tl. These two transmitters share the lane equally.

Obviously at the receiving station B it is necessary to provide some means of determining from which transmitter each character signal originated and to distribute the received signals to their proper destination. If the number of transmitters assigned to the C-channel of the multiplex system was fixed it would only be necessary to distribute the signals in succession to a corresponding number of receivers. However, sincethe signals may originate at one or more of the large group of transmitters in a variable manner, it is necessary to vary the distribution of the signals at the receiving station in accordance with the variations in the assignments of the transmitters at the transmitting station. This is accomplished through a receiving mixer RM maintained in phase with the transmitting mixer TM. The construction of the receiving mixer is identical with that of the transmitting mixer, but the brush B'l thereof is set back one segment relative to brush B4.

RD and distributed by the C-channel segments of ring 26 to a bank of polar relays 21 which store the received combination and apply it to segments I to of ring 28 of each of the startstop distributors D'l, D'2, D'3, etc. The correspondingly numbered segments of ring .28 of these distributors are connected to the selecting magnets 3| of the receiving printers, Pl, P2, P8, etc. Segment 6 of each distributor applies the pulse for the operating magnet 32 of each printer. The brushes B I, 3'2, 3'3, etc. of these distributors are normally held at rest on segment R by individual latches controlled by the release magnets M l, M'2, M'3, etc. These magnets have one terminal connected to the segments S'l, 8'2, 8'3, of the receiving mixer through the control switches C'i, C'2 and C! respectively, the opposite terminals of the magnets being joined to the local segment II of ring 3| of the multiplex distributor.

The multiplex distributors TD and RD are maintained in synchronism in accordance with usual multiplex practice and the brushes Bi and B'5 thereof may be considered to cross the segments of the C-channel simultaneously.

If it is assumed that all of the switches Cl. C2, etc. and UL C'2, etc. are on their contacts IS with brush Bl resting on segment S2 and 'brush B'l resting onsegment SI with a signal combination originating in transmitter T! will be transmitted to line and set-up on the contacts on receiving relay bank 21 and hence on the segments on distributors D'i, D'2, D'3, etc. Immediately thereafter brush B6 engages local segment I! causing brush B4 to move on to segment S3 and releasing brush B2 to set up a combination from the transmitter T2 on relay bank l2. At the same time receiving local rush 3'' engages segment ll', thereby freeing brush B'l which distributes the combination stored in relays 21 to the selecting magnets of printer PI, The brush B'4 passes at this time to segment S'2. Following the transmission of signals from transmitter T2 'on the next revolution of the multiplex distributors the brush B'2 of distributor D'2 is released by the pulse from local segment l1, the circuit being completed through segment S'2, thus causing operation of printer P2. In this manner each of the printers operate in succession following the transmission of signals from their corresponding transmitters.

If it is now desired to close transmitter T2 out it is obvious that the printer P2 must also be eliminated. This is accomplished by moving switch C'2 to its positive contact thereby applying battery to segment 8'2 and causing the brush B! to pass over segment 8'2 without stopping each time it is escaped from segment S'l. If the transmitter T2 and printer P2 are to be cut-out without stopping transmission from the other transmitters, switch C'2 should be operated in proper timed relation to the operation of switch C2. This is effected automatically in the systems shown in Figs. 2, 3, 4 and 5, but in the embodiment of Figure 1, it is contemplated that each of the transmitters TI, T2, T3, etc. are under the control of a common operator, as are printers Pl, P2 and P3. Under such conditions printer maybe entered or closed out of the line manually.

B advising him that at a certain time transmitthe transmitter and corresponding ter T2 will be closed-out. When this time arrives a manual switch 36 in conductor i8 is opened, stopping all the transmitters. The switch C2 is then moved to its positive contact. The attendant at station B, noting that his printers have ceased operation throws switch C'2 to its positive contact. The switch 36 is then closed causing transmitters TI and T3 to operate alternately. At the receiving station printers PI and P3 also operate alternately, but since the receiving mixer was not stopped it may be out of phase with the transmitting mixer thereby causing signals from transmitter TI to be received on printer P3 and signals from transmitter T3 to be received on printer PI. He notes the operation of these printers and if they are not in synchronism with the transmitters, as may be determined by a test character or series of characters sent over one or the other of the transmitters Tl or T3, he immediately opens the manual switch 31, in circuit with local segment l1 thereby preventing the release of the brush arm B4 during one revolution of the multiple distributor and changing the relative position of brush 3'4 with respect to the brush arm of the transmitting mixer, to thereby restore the proper phase relation between the transmitters and the printers.

The. printers PI and P3 once phased with the transmitters TI and T3 are maintained in proper relation therewith by the mixers 'IMand RM respectively.

When it is desired to restore the transmitter T2 and the printer P2 into operation, the attendant at station A transmits another message through either transmitter Tl or T3, advising the receivi'ig attendant at station B of the desired change in the assignments. The switch 36 at the transmitting station is then opened interrupting all transmission and the attendant at each station closes the switch C2 and C2 respectively, to the contacts l9 after which switch 36 is again closed restoring transmission. The receiving attendant then phases the receiving printers with the incoming signals by means of switch 31 and operation is resumed on the basis of three sub-channel operation.

It will be noted from the foregoing that the number of transmitters and printers in operation,

over a single channel. of the multiplex distributor is dependent only upon the positions of the switches Cl, C2, etc. and Ci, C'2, etc. at the transmitting and receiving stations respectively.

While in the system described the switches Cl, C2, etc. and C' l, C'2, etc., are operated manually, in the system shown in Figure 2 I have shown an arrangement for cutting the transmitters and printers in and out automatically. In Figure 2 the start-stop distributors Di, D2, D3, and the receiving start-stop distributors D'l, D'2, US, have been omitted, the tape transmitters directly operating the storage relays at the transmitting station and the multiplex distributor at the receiving station operating directly into the storage relay bank.

Referring now to Figure 2, the tape transmitters Ta, Tb and To are shown each having a marking bus bar M, provided with positive battery through the winding 4| of polar relays Ra, Rb, Rc, respectively, and having a spacing bus bar S with insulated contacts. The tongues of each transmitter are connected through the windings 42 of a common relay bank 43 to ground. The tongues of relay bank 43 are connected to the segments of one channel of a multiplex'transmitting distributor TDI, having a solid ring 44 connected to the apex of the outgoing line Ll. The distributor TDI has a local ring 45, provided with two spaced local segments 46 and 41. Local segment 46 is connected through the auxiliary windings 48 of relay 43 to ground, these windings being poled so as to restore the contacts to their spacing side each time a local pulse is produced from this segment.

The control apparatus for each transmitter Ta, Tb and To is identical and therefore only that associated with transmitter Ta will be described. The tape transmitter Ta has a stepping magnet SM, one terminal of which is connected to positive battery and the other terminal of which is connected to the midpoint of the winding of differential relay DR. The opposite terminals of the winding of the relay DR are joined through auto-control contacts 49 and relay contacts 50 respectively, to the right contact 5| of relay Ra. The two armatures 52 and 53 of relay DR are normally released to the left, whereby contacts 50 and 54 are closed. Armature 52 is connected to ground and armature 53 is connected through the operating winding 55 of relay Sa and thence to the left contact of tongue 56 of a polar relay Qa. Relay Sa has a locking winding 51 and associated locking contact 58 connected in series with a holding t winding 59 on relay Qa and through conduc rs 60 and iii to local segment 46. The operating winding 62 of relay Qa is connected in series with the operating winding 63 and the restoring winding 64 of relay Ra. The opposite terminal of winding 63 is-connected to the left contact of the relay and the opposite terminal of winding 64 is connected through conductor 65 to local segment 41.

A transmitting mixer TMI is common to all of the transmitters and has a segment a, b, 0, etc., individual to each transmitter. Segment a is connected by conductor 66 to tongue 61 of relay Qa. Segment b is similarly connected to the corresponding tongue of relay Qb and segment 0 is similarly connected to relay Q0. The solid ring 68 of the transmitting mixer TMI is grounded through the release magnet 69.

In addition to the mixer, I have provided a 'sending clock SC, common to all of the transmitters, having two sets of segments a and a". individual to the transmitter Ta; 17' and b" individual to transmitter Tb, and c and c" individual to transmitter Tc. The solid ring ill of the sending clock is grounded. The clock has a stop arm corresponding to each transmitter, one only of the stop arms being provided with a pair of brushes B1. The release magnet ll of the sending clock has its ungrounded terminal connected through conductors l2 and 6i to local segment 46.

The operation of the transmitting mechanism is as follows:

Assume all transmitters Ta, Tb, Tc, etc., to have a copious supply of tape, with auto-control contacts 49 closed and the tongues of relays Ra, Rb, etc., and Qa, Qb, etc., on their right hand contacts with all other relays in their unoperated positions. Also assume brush B8 of the transmitting mixer TMI to be at rest on segment a and local brush Bill of the multiplex distributor TDI to be approaching local segment 46. As brush BIO engages this segment a local .pulse will be" sent over the following paths: (1) the windings 48 of relays 43 in a spacing direction; (2) over conductors 6i and 12 to the release magnet ll of the sending clock SC, releasing the brush B1 thereof to pass on to its next group of segments: (3) over conductor 6|, tongue and left contact of relay 13 (common to all of the transmitters) conductor l4, winding I of relay Ra and the right contact and tongue 61 of relay Qa and thence by way of conductor 66 to segment a of the transmitting mixer and by brush B8 and solid ring 68 to the release magnet 69 and to ground.

The completion of this last circuit releases brush arm B8 to pass on to segment band removes ground at the tongue of relay'Ra from the stepping magnet SM releasing this magnet and permitting the contacts of the transmitter Ta to move upwardly, as will be understood by reference to the Benjamin patent aforesaid, momentarily setting up a combination on the tongues of the transmitter Ta. Since all code combinations, except the blank signal which is used for special purpose as hereinafter described, have at least one marking impulse, one of the tongues of the transmitter Ta will engage the marking bus bar M completing a circuit from battery through winding 4| of relay Ra, bus bar M, one or more of the tongues of the transmitter and the corresponding windings 42 of relay 43 to ground. The completion of this circuit sets up the combination on the tongues of relays 43 and energizes relay Ra to restore its tongue to contact 5| reapplying ground to the stepping magnet SM through the windings of the differential relay DR. The magnet SM therefore again withdraws the pins of the transmitter from enchannel associated with the transmitters Ta, Tb,

etc. sending the combination applied thereto by transmitter Ta, over the multiplex line Ll.

On the next. engagementof brush Bio with local segment 46 similar circuits are completed through: (1) windings 48 of relay 43; (2) release magnet ll of theclock SC; and (3) winding 15 of relay Rb, this latter circuit being grounded through the segment bof the mixer TMI. A character from the transmitter Tb is therefore set up on the relay bank 43 for subsequent transmission to line and brush B8 of the mixer TM! is advanced on to segment 0. In this manner each of the transmitters Ta, Tb and To operate in succession as long as each has a supply of tape.

If new thesupply of tape to one of the transmitters becomes exhausted as for instance transmitter Ta, its auto-control contacts 49 will open. This occurs of course when transmitter Ta steps following the setting up of a new character on relays 43, just after local segment 46 has been crossed, with brush B8 on segment a of the mixer TMI. The opening of contact 49 diverts the current flowing through the stepping magnet SM entirely through the left hand winding of the differential relay DR unbalancing the relay and causing the armatures 52 and 53 to be operated thereby applying a locking ground to the stepping magnet through armature 52 and opening contacts 54 at armature 53. As the brushes B9 and BIG complete their revolution the code set up in relays 43 is sent over the multiplex line. When it is again turn for the transmitter Ta to transmit, the passage of brush BIO on to local segment 46 restores the tongues of relay 43 to their spacing side setting up a blank or all spacing signal on the segment of the multiplex distributor 'I'Dl. The circuit completed from local segment 46 over conductor GI and the tongue of Y The purpose of this spacing combination at the receiving station is to close-out the printer associated with the transmitter Ta. Since none of the tongues of the transmitter Ta is permitted to move to its marking side at this time, the restoring circuit for relay Ra, through winding 4| is not completed and the tongue of the relay remains on its left hand side in which position it was operated by the local impulse. Consequently as brush Bill moves on to local segment 41 a circuit is completed from ground at the tongue of relay Ra, the left contact thereof, winding. 63 of relay Ra, winding 62 of relay Qa and winding 64 of relay Ra, and thence byconductor 65 to local segment 41. and by way ofbrush Blll to battery. The windings 63 and 64 of relay-Ra are in opposition to each other but winding 63 predominates as long as the brush Bill is on segment 41, the current through the winding 63 being in such direction as to maintain the tongue of the relay on its left contact. However as soon as brush Blll leaves segment 41 the condenser discharges through the winding 64 restoring the tongue to its right hand contact 5|.

The current through winding 62' of relay Qa moves'the tongues to this relay to their left contacts applying battery through tongue 61 to segment a of the transmitting mixer. Battery is also applied to winding 55 of relay Sa at the tongue 56 of relay Qa, the circuit for winding 55 being incompleted at the armature 53 of the differential relay DR, which is open at this time,

and therefore relay Sa does not operate. The application of positive battery to segment a completes the closing-out of the transmitter Ta since upon each subsequent revolution of the brush B8 of the mixer TMI it passes directly over the segment a coming to rest only on segments b and c and therefore enablingonly the transmitters Tb and Te to operate over the line Ll.

The sending clock SC performs no function during the normal operation of the transmitters nor in the closing-out of a transmitter from service but acts to time the re-entry of a transmitter. It will be noted that the release magnet H of the sending clock is connected directly to the local segment 46 of the multiplex distributor so that it receives an impulse for each revolution of the distributor and is stepped over one pair of segments for each of such local impulses. At no time is battery applied to any of the segments to cause the brush to move past a normal stopcase of the transmitting mixer TMI.

the mixer and the clock are not necessarily in step.

When it is desired to enter a station on the line, as for instance the station Ta previously closed-out, the auto-control contacts 48 of the transmitter Ta are closed by accumulation of the tape loop thereby grounding both sides of the relay DR causing a balance to be produced through the windings of the relay and releasing the armatures 52 and 53 thereof. This may occur of course with the brush B1 of the clock SC in any of its positions. Eventually however the brush B1 is stepped around to the a, a" segments and as it is escaped thereon from segment it first passes over segment a coming to rest on segment a". As it crosses segment a, ground is applied through solid ring and brush B1 to the conductor I6 and thence over contacts 54 and armature 53 of relay DR and through the winding 55 of relay Sa and the left contact and tongue 56 of relay Qa to positive battery. Relay S0 is thus operated, locking up over its contact 11. As brush Bl engages segment a" ground is applied through the solid ring 10, segment a", conductor 18, armature 19 of relay Sn. and conductor 8| to the winding of relay l3 and to positive battery, moving the tongue of this relay to its right hand side. On receipt of the first local impulse on segment 46 following these operations, the impulse is transmitted over conductor 6|, the tongue and right contact of'relay I3 and conductor 82 to the fourth winding 42 of relay 43 in a marking direction-and in opposition .to the impulse supplied at the same time from segment 46 through the windings 48 of this relay in a spacing direction. Due to the resistance 83 in circuit with the windings 48 the current through the windings 42 always predominates so that the tongue of the number four relay is moved to its marking side and the tongues of theremaining relays are set on their spacing sides. The marking force of coils 42 is always greater than the spacing resetting force through windings 48 so that the marking force always prevails, should the two opposing forces be applied simultaneously. This combination, having the number four impulse marking, is thus set up on the segments-of the transmitter TDI Since the tongue of relay I3 is on its righthand side at this time the local impulse does not reach the segments of the transmitting mixer TMI and consequently the mixer remains at rest for this cycle of operation. The local impulse does find a path, however over conductors 6| and 68 to winding 59 of relay Qa and winding 51 of relay Sa to ground at tongue 58 of this latter relay, thereby restoring relay Qa to its right hand side and removing battery at contact 61 of this relay from segment a of the transmitting mixer. The winding 51 of relay Sa merely retains this relay on its right hand side until the foregoing operation is completed. With relay Qa restored to its right side the transmitter Ta is completely entered on the line.

The special code combination with the fourth impulse marking is now set up on the multiplex distributor. On the next revolution of the multiplex distributor this combination is sent over the line LI and serves at the receiving station to enter the printer associated with the transmitter Ta. 7

It should be noted that the entry of transmitter Ta may occur with the mixer TMI in any po-' sition, the mixer being held in that position for the entering cycle. As the mixed continues to revolve following the entry of the transmitter Ta. it will eventually reach segment a at which time the first character code combination will be set up in the storage bank 43 from the transmitter Ta in the ordinary manner. One purpose of this arrangement is to facilitate re-synchronism of the transmitting and receiving mixers if they should lose step for any reason; for example, during a long period when the channels are all idle or as a result of line or apparatus trouble. Mixer synchronism is thus obtained or confirmed whenever transmission is stopped and resumed. This can be done when necessary or at predetermined times.

It will be noted that the closing-out of a transmitter is always followed by the transmission of a blank or all spacing signal over the line as the concluding signal from that transmitter and that the entry of a new station is preceded by the transmission of a special entry code combination having the fourth impulse marking, occuring whenever the brush of the clock SC is on the segments corresponding to the transmitter being entered. With these conditions in mind, the receiving apparatus at the distant station will be described.

Signals transmitted over the line Ll are received upon the solid ring 84 of the multiplex receiving distributor RBI and distributed to the relays of a coding bank CB and a storage bank SB. The tongues of the storage bank SB are connected over conductors 85, which are multipled to the switch arms 86 of a number of multicontact switches controlled by magnets 81. The contacts of the switch arms 86 are connected through the selecting magnets 88 of each of the receiving printers Pa, Pb, and Fe. Each printer has associated with it a cut-out relay COa, COb, etc. provided with two windings 89 and 8| and a single tongue 92.

The tongues of the control bank of relays CB are coded so as to supply negative battery to a conductor 83 whenever the blank or all-spacing combination is received and to apply the same battery to a conductor 94 whenever the entry code combination having the fourth impulse marking is received. The winding 95 of an entry relay E is included in the conductor 84.

At the receiving station there is also a receiving mixer RMI and a receiving clock RC, common to all of the printers. The mixer RMI is provided with a pair of segments for each printer, each pair comprising a long segment al, bl, cl, and a short segment a2, b2, c2. The solid ring of the receiving mixer is connected through the release magnet 96 to ground. Segment al is connected to the tongue 2 of relay CO1 and segments bl and cl are connected to the tongue of the corresponding relay COb, Got. The short segment at is connected to the winding 89 of relay COa multipled to the conductor 93 and the segments b2 and 02 are similarly connected to the corresponding winding of relays CO1, and CO0, also multipled to conductor 93.

The receiving clock RC has three segments a3, b3 and 03, each connected to one terminal of the winding 9| of the relay COa, CO, (30c, respectively.

The operation of the receiving apparatus is as follows: Assume each of the transmitters Ta, Tb and To to be transmitting over the channel with the brush Bil of the receiving mixer RMI on segment al and the combination from the transmitter Ta to have just been received and stored in the storage bank SB. Then as brush magnet 91 closes the contacts 86 and a sixth pulse contact I00, operating the selecting magnets 80 of the printer in accordance with the combination stored in relay bank SB and energizing the operating magnet l| of the printer to effect the printer operation. The printer Pa therefore records the character transmitted by the transmitter Ta.

As brushes BI! and Bl3 continue their revolution crossing the code segments I to 5, a character from transmitter Tb is set up on the bank SB and immediately thereafter as brush B12 again engages local segment 91, this character is recorded on the printer Pb. At the same time brush Bl I of the receiving mixer RM! and brush B of the receiving clock move into the succeeding positions.

If now transmitter Ta is closed-out, such condition is indicated by the reception of a spacing code combination at a time when the brush BH rests on segment al. This code combination is set up on the storage bank SB and on the control bank CB. As stated, the control bank CB is coded so as to apply negative battery to the conductor 93, at this time preparing a circuit through winding 89 of relay CO8 to segment (12 of the receiving mixer. As the next local impulse occurs the magnet 81 associated with printer Pa operates, but since the signal is of an allspacing character, it is deleted by the cut-out mechanism normally forming a part of the printer mechanism. Brushes Bil and B are escaped at the same time and as brush .BH crosses the small segment a2 it completes the circuit previously prepared through the winding 89 of relay CO8, moving the tongue 92 to its right hand or positive contact, thereby applying positive battery continuously to segment at and closing out printer Pa from further operation due to the continuous passage of the brush Bil over segment al and a2 upon subsequent revolutions of the brush arm.

Succeeding signals transmitted by transmitters Tb and To are therefore received only on printers Pb and Po, respectively.

If transmitter Ta is to be entered on the circuit again such operation will be indicated at the receiving station by the reception of the entry code combination having the fourth impulse marking.

sion of this entry code combination. A circuit for the local pulse is completed, however, over conductor 99 and the left contact and tongueof relay 95 to solid ring I02 of the receiving clock and thence by brush B l 4 and segment a3 to winding 9| of the relay C05 in a direction to restore the tongue 92 to its left hand contact, thus removing positive battery from segment 9| of the receiving mixer RMI. Consequently the printer Pa is again restored to the circuit so that it will respond to subsequent signals transmitted from the transmitter Ta.

In this same manner any of the printers may be cut in or out of the circuit following the discontinuance of the operation or the restarting of any of the transmitters.

It will be noted that each transmitter and corresponding printer are entered at the time of the first engagement of the brushes of the receiving and transmitting clocks on the segments corresponding to the transmitter and printer to be entered. They do not start transmitting and receiving signals, however, other than the entry code signal until the transmitter and receiving mixers have been stepped around to the position corresponding to such entering transmitters and printers. Since this type of ehtry involves both a time element and the transmission and reception of a code signal, I have termed it for convenience time-code entry. The function of entry involves selection of one of a number of receiving devices or channels, and the selecting means shown and described above is the equiva- This will occur only when the brush BM of the on receiving clock RC is at rest on segment a3, since the receiving clock and the sending clock are both invariably stepped ahead one position upon each revolution of the multiplex distributors and therefore maintained in exact phase relation.

The entry code combination applies negative battery to the winding 95 of relay ER operating the same to its left hand contact thereby disconnecting the local segment 91 from the conductor 99 so that none of the circuits through the segments of the receiving mixer are completed and the receiving mixer is held at restin its last position in the same manner that the transmitting mixer TMI was held at rest during the transmislent of ordinary code selection but has the additional advantage of higher efficiency by permitting the transmission of character signals between the selection or entry signals.

A different type of entry, which I have termed time and turn entry, is effected only when the brushes of the clock and the mixers simultaneously engage the segments associated with a particular entering transmitter and printer. This latter type of entry is shown in Figures 3, 4 and 5.

Only three transmitters and receiving printers have been shown in the foregoing example but the number may be expanded indefinitely. For instance 1000 or more outlying stations, each having only a few messages a day may share a single channel or lane of trafiic between say New York and Chicago. Each of these outlying stations will have the equivalent of a direct line' connection between the stations thereby enabling messages to be transmitted at any time from any of the stations. With a large group of such substations assigned to a channel, the load will be distributed fairly evenly throughout the day and ordinarily only a few of the stations will betransmitting at any instant. Therefore the rate of transmission from any station will be fairly good. If for any reason a considerable number of such stations desire to use the channel simultaneously, the rate of transmission from each station will be reduced until the congestion is relieved but the direct line facility will not be otherwise interfered with. Where a. large number of sub-stations associated with each of the main stations are assigned to a single lane of traflic extending between the main stations, extended channel equipment is obviously required. An expanding channel system involving the extension of the sub-channels to individual substations is shown in Figs. 3, 4 and 5 and will now be described.

In Figure 3 the transmitting equipment at three branch ofllces or sub-stations X, Y and Z is I shown. Obviously any number of such stations may be provided. The equipment at each station is identical and therefore only that provided at one of these stations will be described.

The transmitting equipment comprises a tape transmitter'Tx the contacts of which are connected through the windings of a relay bank RBx to the numbered segments of ring I05 of a startstop distributor Dx. The ring I05 also has a rest segment R connected to marking battery through the winding of a marginal relay MRx and a start segment S conencted to spacing battery. The solid ring I08 is connected to a sending line SLx extending to central office equipment shown in Figure 4. The distributor Dx has a pair of local rings I01 and I08, the former having a local segment I and the latter being connected to positive battery. The brushes BIS and BIG are normally held at rest by the latch L controlled by the start magnet M. Magnet M is controlled through the tongue and the front or make contact of relay MRx.

The ungrounded terminal of the stepping magnet SM of transmitter Tx is connected to the midpoint of the winding of a differential relay DR. one end of which is connected through normally closed contacts III to the local segment I09 of ring I01. The opposite end of the winding of relay DR is connected through the normally closed contacts II2 of a control relay CRx to segment I09. Relay CRx has a second tongue li3'joined by conductor II5 to the lowermost tongue of relay bank RBx and thence through the remaining tongues, when they are all on their spacing contacts, to the receiving line RLx extending from the central station. The line RLx has a receiving relay LRx in circuit therewith and normally terminates at ground through a resistance Rx. However, when the contacts of relay bank RBx are all on their spacing sides and relay CRx is energized in order to ground its tongue II3, the resistance Rx is shunted out of the line RLx, the line being grounded through the conductor II5. Relay CRx is controlled by the auto-control contacts IIG whenever the tape loop II1 decreases to a predetermined minimum as is well understood in the art.

Before describing the operation of the transmitting apparatus it will be well to consider the apparatus" at the central station indicated as station C (Fig. 4). This station is provided with a multiplex distributor MD having a set of transmitting rings TR transversed by a'brush Bil, a set of receiving rings RR provided with a brush BI8 and a set of local rings LR having a brush BIS. Segments I to 5 of one channel of the transmitting ring TR which by way of example may be the C-channel, are connected to the tongues of a bank of polar transmitting relays PTR. The ungrounded terminals of the windings of relays PTR are connected in series with the main or left hand winding of a set of polar control relays Rx and thence to segments I to 5 of the receiving ring of a startstop distributor D'x. The solid ring of distributor D'x is joined to the sending line SLx through a resistance H8. The brush B20 of distributor D'x is normally held on rest segment R by .a latch controlled by the startv magnet M'x. The rest segment of distributor Dx is grounded through the winding of a relay II3 having its spacing contact S connected to the ungrounded terminal of the starting magnet M'x. The tongues of relays Rx, when they are all on their spacing side, apply ground to a conductor I2I connected to one terminal'of the main winding I22 of a relay Lx. Relay Lx has a. holding winding I23, one terminal of which is connected by conductor I24 to local segment I25 of the multiplex rings LR and the opposite terminal of which is connected through the windings of relays Nx and Mx to the right and normayy closed or break contact of relay Kx and thence by way of conductor I20 to segment a: of the transmitting mixer TM2. Relay Lx has two tongues I21 and I20, the former of which applies battery to relay Kx whenever relay Lx is energized. 'The tongue I23 normally rests on its right contact which is connected to local segment I25 and when the relay is energized, engages its left contact to shunt out the winding of relay Mx.

The tongue and operated contact of relay Mx serve to shunt out the resistance II8 included in the line SLx, over conductors I29 and I3I, whenever relay Mx is energized. Relay Nx when energized applies positive battery by way of conductor I32 to the auxiliary or right hand windings, in series, of relays Rx and P'IR, to move the tongues of relays I, 2, 3 and 5 thereof to their spacing contacts and the tongue of relay 4 to its marking contact, thereby at the contacts of relays Rx removing ground from the relay Lx and through the contacts of relays PTR setting up an entry code combination on the segments of transmitting ring TR of the multiplex distributor.

The circuit for relay Kx is completed from tongue I21 of relay Lx when the latter relay is energized, through normally closed contact I33 of relay Ix. Relay Ix has a main winding I34 and a locking winding-I35. The main winding is connected between the tongue of a marginal relay Jx and a short segment 1: of a sending clock SC. The locking winding of relay Ix is connected between the locking contact I30 of the relay and a large segment :r" of the sending clock.

The clock SC is similar in construction to the transmitting mixer TM2, each having a single pair of brushes B2I and B22 respectively, mounted upon one of the stop arms of which there is one provided for each station X, Y and Z, etc., assigned to the particular lane of traillc. The start magnet I38 of the sending clock SC is controlled over conductor I39 from the local segment I25 of the multiplex distributor.

Each of the stations Y and Z also have at the central station C a receiving distributor D'y, D'z, and a group of relays I, J, K, L, M and N. The windings of the 111 relay are connected to segments 11' and y" of the sending clock by conductors I and I42, and the windings of relay 12 are connected to segments 2' and .2" thereof by conductors I43 and I44. Similarly the tongues I45 and I46 respectively, of the relays Ky and K2 are connected to se ments 3/ and 2, respectively, of the transmitting mixer TM2 over conductors I41 and I48. The relays Ky and K2 each have an additional tongue I49 and I 5i, respectively, connected as follows: the left or operated contact of the tongues I45 and I 46 of relays Ky and K2 are connected to positive battery and the right or normally closed contact of tongues I49 and I5I are also connected to positive battery. The tongue I43 is Joined to the operating or left hand contact of relay Ka: and the left contact of tongue I43 is joined to the tongue I5I of relay Kz. The left contact of tongue I5I is connected to the local segment I25 over the conductor I39. The purpose of these connections will appear in the description of the operation of the system.

The segments of the G-channel of the receiving rings RR of the multiplex distributor are connected to the windings of two banks PCR and PRR, of polar relays in series. The contacts of relays PCR control the receiving channelling mechanism and their function will be described in connection with Figure 5. The contacts of the polar receiving relays PRR are multiplied to the segments I to of a group of start-stop transmitting distributors, one only TD; of which is shown, one of these distributors being provided for each of the substations X, Y, Z, etc. These distributors are more fully described with reference to Figure 5.

The distributor TDzc has in addition to the numbered code segments, a rest segment R and a start segment S. The solid ring of the distributor is connected to the winding of a polar relay I52. The tongue of this relay is joined to the outgoing line RL. The marking and spacing contacts of relay I52 are connected respectively to the windings I53 and I54 of relay Jx, these windings being so arranged that current through either one of them tends to move the tongue of the relay to its grounded contact. The relay is marginal, however, so that it does not operate on the normal current flow therethrough.

With the above circuit arrangements in mind, the operation of the transmitting mechanism at stations X, Y and Z and the associated mechanism at station C will be described.

Assume that each of the stations X, Y, and Z are operating and the last character was transmitted from station Z. The brush B2I of the transmitting mixer 'IMz will be at rest on the a? segment at this time. As local brush BI3 of the multiplex distributor MD engages local segment I25 a pulse will be sent out over two paths, (1) conductor I39 and the escapement magnet I38 of the sending clock SC allowing the clock to step one set of segments; (2) through the tongue 828 of relay Lx, winding of relay Mr and the tongue and right hand contact of relay K; and thence by conductor I25 to the a: segment of the mixer 'IMz and by way of the brushes B2i to the release magnet I55, stepping brushBZi on to the y segment, and at the same time operating relay Mx to its left contact and thereby shortcircuiting the resistance I I8 in the line SLx extending from the branch office X. The shunting of the resistance H8 increases the current in the line SL1; over the circuit extending from negative battery at one terminal of the winding of relay MRX (Fig. 3), thence by segment R of distributor Dx brush BI5, line S111: and brushes 1320 (Fig. 4) to the winding of relay I I9 and thence to ground. The current flowing through relay H3 at this time being in a marking direction, maintains its tongue on its dead contact M.

The relay MRX is marginal and responds to the increase current caused by shunting out resistance I I8, thereby completing a circuit for the start magnet M of distributor Dx. Brushes BI5 and BIG are thus released passing over the start segment S and the five code segments associated with the transmitter TX. As local brush BIB leaves segment I09 battery is removed from the stepping magnet SM permitting the tape pins to rise and setting up a combination on the segments I to 5 and thereby enabling brush BI5 to transmit a start impulse followed by live code impulses over line Sim.

The start impulse received on the distributor D: at station C operates the relay II3 to its spacing side completing a circuit for the start magnet M'x of distributor D): and releasing the brush .820 which crosses its code segments in phase with brush BI5 of distributor Dx. Consequently the combination set up on the tapetransmitter Tx is distributed to the relays Rx and PTR in series. If this combination is anything except an all spacing combination the contacts of relay Rx are left open at one point and these relays serve no useful purpose at this. time. The relays PTR, however, through their contacts set up the received combination on the segments of the transmitting ring TR of the multiplex distributor. As the multiplex transmitting brush BII completes a revolution, the combination just set up on the segments of the C-channel are sent over the multiplex line ML to the receiving station.

Immediately thereafter as local segment I25 is again crossed, another impulse is applied to magnet I38 of the sending clock SC and through relay My, tongue I of relay Ky and segment :1; of the transmitting mixer TlVIz to the start magnet I stepping the mixerbrushes on to segment .2. Relay My shortcircuits resistance I I8 associated with line SL releasing the brushes of the Dy distributor at station Y to transmit a character from this station, for subsequent transmission over the multiplex transmitter MD.

Similarly the next local impulse from segment I25 operates relay Mx to release a character from station Z at the same time stepping the clock SC and the mixer TMz forward one step.

This operation continues as long as each of the stations X, Y and Z have material to transmit. However, if the supply of tape at one of the transmitters, for instance at station X, becomes exhausted, auto-control contacts I'IGare opened deenergizing relay CRx and'opening its contacts H2 and H3. The opening of contact H2 causes battery from ring I08 and segment m9 of distributor Dx to be diverted through right hand winding only of differential relay DR to the stepping magnet SM. Relay DR is therefore operated its armature I55 opening contact III and applying locking battery to the relay DR and the stepping magnet SM. The pins of the transmitter TX are therefore held depressed continuously and therefore retained on their spacing bus bar.

As local brush BIQ of the multiplex distributor MD again crosses local segment I25 following the transmission of a character from station Z, that is with brush B2 I on segment a: of the transmitting mixed TN2, the relay Mx will be again operated to short circuit resistance II8, releasing the brushes of distributor Dx, thus causing the all spacing signal set up on the tongues of transmitter TX to be transmitted over the line SLX and to be eventually set up on the segments of the multiplex distributor ring TR. At the same time the relays of bank RBx (at station as) are all moved to their spacing sides thereby connecting conductor II5 to the receiving line RLX. This all spacing or blank signal operates the relays RX at station 0 to their spacing sides thereby applying ground over conductor I2I to winding I22 of relay Lx operating the tongues of this relay to their left hand sides. Tongue I2'I applies battery to relay Kx which in turn moves its tongue to its left hand side. when this occurs positive battery normally applied to tongue I49 of relay Ky is extended over the tongue of relay Ks and conductor I23 to segment a: of the transmitting mixer TMz. Consequently each time the brush B2I of the mixer engages segment a: it completes a circuit for the release magnet I55. thereby withdrawing the stop-arm and permitting brush B2I to rotate directly past the a: segment, on to the 1! segment. The station X therefore loses its turn and transmission takes place alternately from stations Y and Z.

If the supply of tape at station Y should now become exhausted this station will be cut out in a similar manner, first transmitting a blank or all spacing signal over the line thereby setting the contacts of relays R on their spacing sides and applying ground to winding I22 of relay L As outlined above this causes the operation of relay Ky whereby its tongues are all moved to their left hand sides. When this occurs positive battery is applied to segment a: of the transmitting mixer TM: from the right contact and tongue I 5I of relay Kz, left contact and tongue I43 of relay K and left contact and tongue of relay Kr, and thence by conductor I26 to segment 1:. Battery is also supplied to segment 1 of the transmitting mixer T1VI2 from the left contact. and tongue I45 of relay K and conductor I41 to segment 1 With stations X and Y both discontinued, a character is transmitted from station Z for each revolution of the multiplex distributor.

If the tape supply at station Z should now become exhausted this transmitter will first send a blank signal and as a result thereof apply ground from the contacts of relays R1 to the winding I22 of relay Lz, which latter relay causes the operation of relay K:- As the tongues of this relay engage their left hand contacts battery for station X is obtained from the local segment I25 through tongue I5I of relay Kz, the left contact of tongue I49 of relay Ky and thence through tongue of relay Kx to segment a. Battery for segment 1 is obtained from the source previously traced and battery for segment 2: is obtained from the left contact and tongue I46 of relay K1.

With all stations closed out it is obvious that the C-channel will be idle and brush B2I stopped each revolution on the .1: segment being released therefrom by each local impulse from segment I25. The transmitting mechanism at station X will not be released, however, since the circuit for relay Mx is open at the right contact of relay Kx.

The angular speed of the transmitting mixer brush BZI should be equal to or greater than the angular speed of the multiplex distributor brushes in order that it may complete its revolution in a time no greater than that required by the multiplex distributor. The series circuit from the local segment I25 through the left contacts and lower tongues of relays K1, Ky and Kx to segment a: of the transmitting mixer is mainly for the purpose of preventing the stop arm of brush B2I from engaging the brush in an uncertain manner after a period when no transmitters are operating. Thus it is seen that automatic synchronism of the expanding channels on the mixers is secured when they return to operation after a period when all channels are idle. This provides a method of self-synchronization since all channels can be stopped during line trouble and resume operation in phase when the trouble clears.

It should be noted that the sending clock SC is controlled directly from the local segment I25 and therefore is stepped once for each revolution of the multiplex distributor, whereas the brush B2I of the transmitting mixer 'IMz, in case station X is not operating, passes directly from segment Z to segment Y, and in case both stations X and Y are not operating the brush B2I passes from segment Z around to the same segment again. The clock SC and transmitting mixer TM: therefore are not maintained in step. The purpose of the sending clock SC is to enable a station to be entered on the line again, when it is desired to resume operation thereof, in proper timed relation with the reassociation of its receiving mechanism with the line at the receiving station. Therefore it is necessary to maintain the clock SC in synchronism with a corresponding clock at the receiving station. Since the transmitting and receiving distributors at each station are maintained in synchronism continuously and since the clock SC and the corresponding receiving clock to be described here-' inafter are both stepped directly from the transmitting and receiving distributors the clocks are maintained in synchronism.

It now it is desired to restore the transmitter into operation at one of the sub-stations, for instance station X, due to an increase in the size of the loop of tape III the station will be entered automatically in the following manner. The increase of the loop III closes contacts IIG, thereby operating relay CRX and closing its contacts III and H3. When this occurs current from local segment I03 of the distributor Dx passes through the left winding of the differential relay DR balancing that in the right winding and releasing the armature I56. Current for the stepping magnet SM is thus provided solely from the local segment I09. It will be recalled that at the time station X was discontinued from operation,

'polar relays RBX were moved to their spacing side, connecting the conductor I I5 directly to the line R112. The closure of tongue I I3 of relay CRX now applies ground to the line RLX over the conductor II5, thus short circuiting the resistance Rx which is normally in the line RLX, thereby increasing the current fiowing over the line RLX from either the marking or spacing contact of relay I52 at station C and hence increasing the current through either the winding I53 or I54 of relay Jy, depending upon the position of the tongue of the relay I52. Relay Jx is thus operated to apply ground to the winding I34 of the relay Ix. Consequently as the clock SC is stepped around, eventually crossing segment 2:, a circuit will be completed over winding I34 of relay x from the solid ring I31 of the sending clock SC. At this time Ix is operated and an instant later as the brush B22 engages segment x" a locking circuit for relay I1: is established from ring I31 of the clock, brush B22, segment a:" and locking winding I35 of relay Ix to the grounded tongue of the relay. Movement of the tongue of relay Ix away from its normal contact I33 interrupts the circuit for relay Kx, allowing its tongue to return to the righthand contact and thereby removing battery from segment a: of the transmitting mixer TM2.. The brush B2I, it will be recalled, rests on segment a: between each local impulse from the segment I25 of the multiplex distributor MD. On the next crossing of the local segment I 25 following the operation of relay Ix and the release of relay Kx, a local pulse-is sent from segment I25 by way of conductor I24 through locking coil I23 of relay Lx (thereby firmly holding the tongues of the relay on their lefthand side), thence through the winding of relay Nx, tongue I28 and left contact of relay Lx (short circuiting relay Mx). and right contact and tongue of relay Kit to conductor I26 and thence to the :c segment of transmitting mixer TMz and to the escapement magnet I55.

The operation of relay Nx applies battery to the supplemental or right hand windings of relay banks Rx and PTR, which are connected in series in such manner as to move the tongues of relays I, 2, 3 and 5 of each bank to their spacing sides and the tongues of relays 4 to their marking sides. This special combination having the number 4 impulse only of marking character is arbitrarily selected to control the entry of the printer corresponding to the station X at the receiving station. The operation of this control mechanism at the receiving station will be described later in connection with Fig. 5. With this code combination now set up on the contacts of the transmitting ring TR it will be transmitted to the line on the next revolution of the brushes of the multiplex distributor MD.

The operation of the fourth relay of bank Rx to its marking side also interrupts the ground connection to winding I22 of relay Lx, permitting the tongues of this relay to return to their normal righthand side as soon as the holding circuit through winding I23 is interrupted by passage of brush BIS off of local segment I25. The tongue of relay Nx returns to normal simultaneously with the tongues of relay Lx, since their winding are in series. Relay Kx is restored to normal when its winding is deenergized by opening of tongue I21. Relay IX remains operated until the brush B22 of the sending clock SC leaves its segment 3:" when it returns to normal. Relay J: is released on the following revolution of the multiplex local brush BIS, when relay Mx sends a start impulse to outstation :r, which starts distributor Dx and sets up a character on relay bank RBX. Relay Mx has been in its normal unoperated position all the time. With relays Ix, Jx, Kx, Lx, Mx and Nx all in their normal positions the entry of station X is completed.

If now one of the other stations, for instance station Y, desires to resume operation the autocontrol contacts H6 at this station are closed, resulting in the operation of relay Jy to its grounded side as described with reference to relay Jx and thereby causing relay Iy to be operated th first time that the brush B22 of the sending clock crosses segment 11' and comes to rest on segment 3 The operation of relay I releases relay Ky removing the battery from the 1/ segment of the transmitting mixer 'IMz so that -it now comes to rest on the 1! segment following its escapement from the a: segment, the first time that brushes B2! and B22 engage their respective segments 1/ and y" simultaneously. If the brushes of the transmitting mixer TlVIz and the sending clock SC do not engage these segments simultaneously, station Y is not cut in at this time since the battery is removed from segment 1/ only while the brush 22 of the sending clock is on segment 1/". Since th sending clock is advanced one position only for each local impulse, whereas the brush of the transmitting mixer may move over several positions for each local impulse, it is obvious that after a few revolutions of the clock the brushes B22 and B23 will he stepped on to segments 1! and y", respectively, from the same local impulse. When this occurs brush B2I is stopped on segment 11 due to removal of battery from this segment at the contact I45 of relay Ky. Therefore the next local pulse from segment I25 finds a path to ground -two banks PCR and through the winding of relay Ny, tongue I28 and left the contact of relay Ly, right contact and tongue of relay Ky and conductor I" to segment 1/ and thence through the release magnet I to ground. When this circuit is completed station Y is entered, relay Ny causing the movement of the 4th relay of banks Ry and PTR to their marking sides, and the movement of the 1st, 2nd, 3rd and 5th relays to the spacing sides, resulting in the transmission of this special entry code over the line as described with reference to the entry of station X. At the same time relay Ly is released by interruption of its ground at the tongue of the fourth relay of bank Ry or by the completion of the travel of brush BIB over segment I25 and battery is permanently removed from segment 1/ of the transmitting mixer TM; due to the movement of tongue I21 of relay L, away from its left contact, thereby interrupting the circuit over relay Ky (through the contacts of which the battery was supplied to segment y) Similarly station Z may be cut in, this occurringonly when the brushes of the sending clock SC and the transmitting mixer TMz pass on to segment Z and Z concurrently. This type of entry of the transmitting stations into the circuit depending upon positioning of both the clock and mixer I have for convenience termed time and turn entry.

It will be noted that upon closing out a station from the channel, a blank or all spacing signalwas transmitted from the multiplex distributor MD over the multiplex line ML and that on entry of one of the stations, a special entry code combination was transmitted preceding the sending of character code signals from the transmitter. As stated before the blank signal and the special entry combination control the closing out and entry of the receiving apparatus for the associated station at the opposite end of the multiplex line ML. The equipment by which this is accomplished is shown in Fig. 5 and reference will now be had thereto.

The signals received from station C over the line ML are repeated by the relay I6l to the solid ring I 62 of the receiving ring RR of the multiplex receiving distributor MRD. These signals are repeated from the segments of'the c-channel to PRR of polar relays in series. Relays PRR set up the received combination on the segments of each of the start-stop transmitting distributors TDX, TD and the windings I of a multiplex printer MP2. The solid ring of distributor TDX is joined by a line Lx to an associated branch office, a simplex printer located in the central office or to any other destination X. Similarly the solid ring on distributor TDy is connected to a-line Ly extending to sub-station Y. Ihe contacts of relays PCR are coded, both to the blank signal indicating when a station is to be closed-out and to the entry code signal having the fourth impulse marking, which indicates when a station is to be entered. During normal transmission, when neither of these combinations are sent, it performs no function.

Following the reception of a character as from the X transmitter, the local brush B23 engages local segment I63 which sends an impulse over two paths, the first by Way of conductor I64 to the release magnet I65 of the receiving clock RC and the other by way of conductor I66 and normally closed contact I61 of relay I68, thence by conductor I69 to the' release magnet I II of the distributor 'I'Dx and thence by conductors I12 and I13 and the left contact and tongue I16 oi control relay CR; and conductor I16 to the :1 segment of the receiving mixer RM: and by solid ring I16 of the mixer to the release magnet I11. The brushes B26 and B21 of the receiving mixer RM: and receiving clock RC1 thus receive one release pulse for each local impulse from the multiplex distributor.

The release of brush B28 of the distributor TDx transmits the received code combination, with the addition of a rest and start impulse, over the line L1 to the receiving apparatus at the distant end thereof.

If it is assumed that all the stations X, Y and Z are transmitting, then the next received character will come from the transmitter Y. This character code also operates relays PCR and PRR, the combination being set up on each of the transmitting distributors TDX, TDy, and the polar windings I60 of the selecting magnets of printer MP1. The next local pulse from segment I63 escapes the brush of the receiving clock and also completes a circuit over the conductor I66, left contact and tongue of relay I61 and conductor I18 to the release magnet I19 of the transmitting distributor TDy and thence by tongue I8I of control relay CRy to the yr segment of the receiving mixer RM: and thence to the release magnet Ill, advancing the brush B26 on to segment 21, and releasing the brush B29 of the distributor TDy to repeat the combination over the line L In a similar manner the next character received from the transmitting station Z escapes the brushes of the receiving clock RC1 and receiving mixer RM: and completes a circuit for the operating magnet I85 of the printer MP:. It will be understood that the selecting magnets I68 of printer MP1 are polar, thereby responding to the polar signals set up on the contacts of relay bank PRR, or the magnets I68 may be neutral and preceded by individual polar relays. Obviously printers reperforators or storing devices may be used in any of the positions occupied by the distributors TD; and TDy or printer MP1.

This operation continues as long as each of the stations X, Y and Z are transmitting. If any one of these stations is closed-out at the transmitting end, the concluding signal from the station being closed-out will consist of the all spacing combination. Assume that station X is to be closed-out indicated at station D by the reception from station X of a blank or all spacing combination, this will be received upon the relays PCR and PRR and will be set up on the segments of each of the transmitting distributors TDX, T1331, etc. However, since its only function is to control the closing-out of the position of the X station on the receiving mixer RM:, it is not transmitted over the line Lx, but is deleted as will presently appear.

The all spacing combination moves the tongues of each of the relays PCR to their lefthand contacts, thus completing a circuit from ground through the tongues and lefthand contacts of each'relay to conductor I82 and thence to the winding of cutout relay COX, moving the tongues of this relay to their rlghthand sides and short circuiting, through tongue I88, the release magnetill of distributor TDX and preparing a circuit through tongue I84 to the operating winding I85 of relay CRX. As the next local impulse from segment I63 is received, following this blank combination, it finds a path to ground through conductors I66, the tongue I61 of relay I68, tongue I83 of relay COX and thence by way of conductor I13 and tongue I14 of relay CR: and conductor I15 to the :01 segment of receivin mixer'RM: and thence through the release magnet I11 to ground. A part of the local impulse also passes directly through the release magnet I65 of the receiving clock, advancing the brushes of each of these rotary devices one step. The

brush B28 of distributor TDX is notreleased, however, since the magnet I1I is'short-circuited.

Therefore the blank combination is not sent over the line Lx. As the brush B26 escapes from segment :01 of the receiving mixer RMz, it crosses a small segment :02, thereby applying ground 5 through the release magnet I11, ring' I16, brushe es B26 segment a::, conductor I80, tongue I84 of relay COX, which is on its righthand side at this time, to the operating winding I85 of relay CRx and thence to battery. Relay CRX is thus op- 20 erated andlocks up through the winding I85 and tongue I66. The tongue Illof relay CR): upon being moved to its right hand side, applies continuous positive battery to segment :01 of rev "ceiving mixer RM: from the right contact and tongue I88 of relay CR conductor I81 and the right hand contact and tongue I14 of relay CRX and thence to segment an. This circuit is maintained as long as station X is closed out. Consequently each time the brush B26 of the re- 30 ceiving mixer RM: leaves segment 21 it passes directly over the segments x1 and 1:: coming to rest on segment 111. The transmitting distributor TD! is therefore eifectively removed from the circuit and all signals received are distributed as alternately to the distributors rm and TDz.

Similarly if station Y should discontinue transmitting, an all spacing combination would be received as the concluding combination from the Y station transmitter. This combination would operate. relay CO through the circuit established by the relays 'PCR, which in turn would short-circuit the release magnet I18 of distributor TD, and at the same time escape the brush B26 of mixer RM: from segment 1/1 to segment 21. This brush in passing segment 1/: would operate relay CRy to apply battery continuously to the yr segment of the receiving mixer RM: thereby permitting the brush B26 on subsequent revolutions, to pass directly over the yr segment without stopping thereon. With channels X and Y thus eliminated, all signals would be transmitted directly to the printer MP2, this printer receiving one character for each revolution of the multiplex receiving distributor MRD.

If now one of the transmitters, at station X for instance, desires to again transmit, this desire will be signified at receiving station D by the reception of the entry combination having the fourth impulse marking. As explained in connection with the sending clock SC at station C, this impulse always arrives in its proper turn, that is following a character transmitted from station Z at a time when the brush of the receiving clock RC1 is on the 2:: segment. This entry combination is set up on the contacts of relays PCR and PRR., Since it performed no function at the printer, it is also deleted. It completes a circuit, however, from ground through the left contacts and tongues of relays I, 2, 3, and 5 of bank PCR and through the tongue and right contact of relay 4 and thence through the winding of relay I68. This latter relay opens its contacts I61 and closes contacts 76 I88 applying battery through resistance I93 and conductor I89 to the solid ring ISI of the receiving clock RC1, the circuit being completed by way of segment as, on which the brush B21 rests at this time, to the release winding I92 of relay CR}; and to ground through the tongue I86 of the relay. In order to insure releaseof relay CRX at this time, resistance I93 should be equal to or a little less than resistance I94 connected to winding I85 of the relay. This relay upon releasing removes battery at tongue I14 from segment :m of the receiving mixer RMz. Consequently on the next opportunity brush B26 comes to rest on the x1 segment thereby entering the transmitting distributor TDx so that it responds to signals transmitted from station X.

In a similar manner the receiving apparatus corresponding to station Y may be entered, each station assuming its proper place on the channel and the signals therefrom being distributed through the proper distributors TDar, 'I'Dy, etc., to their proper destination. It will be understood of course that the receiving clock RC is kept in step with the sending clock SC, each being re leased one step for-each revolution of the multiplex distributors which are maintained in accurate synchronism and likewise the transmitting mixer TM: and the receiving mixer RM: are kept in step with each other, but not necessarily in step with the clocks. As long as these devices maintain this phase relation any station may be entered or closed out as desired without interrupting transmission or reception from any of the other stations. It will also be apparent that when all channels are cut out, the brush of mixer RM: is stopped and released at X channel in synchronism with the brush of transmitting mixer TMz, providing self-synchronization as pointed out above.

It will be understood of course that the invention may be embodied in various other forms and applied to lanes of trafiic other than a multiplex channel. Therefore I do not desire to be limited to the particular embodiment shown but contemplate all applications of the principles herein set forth. as coming within the scope of the appended claims. No claim is made herein to the broad features involved in repeating signals into or from the expanding channel system, except start stop means or its equivalent, these features forming the subject matter of my copending application Serial No. 106,904, filed October 21, 1936, now Patent No. 2,233,346, issued Feb. 25, 1941. H

What I claim is:

1. In a telegraph system, a plurality of transmitters and a plurality of receivers, one for each transmitter, a single set of transmitting contacts operable in cycles, a sequencing device having means individual to each of said transmitters for operatively and invariably associating one of said transmitters with said contacts during each cycle of operation thereof and selective means for varying the number of transmitters and receivers operable in turn over said contacts.

2. In a telegraph system, a lane of traflic, a plurality of transmitters operating in succession over said lane, means for discontinuing the operation of one of said transmitters and means for transmitting a discontinuing signal condition over said lane of trafiic.

3. In a telegraph system, a lane of tramc, a plurality of transmitters operating in succession over said lane, means for entering additional transmitters on to said lane and means for transmitting an entering signal over said lane preliminary to the entering of an additional transmitter.

4. In a telegraph system, a lane of traffic, a

plurality of transmitters operable in predeter mined order to transmit characters over said lane, means for entering a transmitter 011 to the lane or closing a transmitter from the lane and means for automatically modifying the electrical condition of the lane to indicate when a transmitter'is entered on to or closed therefrom.

5. In a telegraph system, a lane of traiiic,-transmitting and receiving stations at opposite ends of the lane of traffic a plurality of transmitters, means for operatively associating each of said transmitters with said lane of traflic and for closing out each transmitter therefrom, and means for signalling to the receiving station the entry of a transmitter on and the exit of a transmitter y from the lane at the transmitting station.

6. In a telegraph system, a lane of traflic, a plurality of transmitters operatively associated with said lane and normally occupying the full lane time, a mixer for determining the order of operation of said transmitters, means for preparing an additional transmitter for entry on to the lane and a timing device for operatively associating said additional transmitter with said mixer whereby it will share said lane with said other transmitters. v

7. In a telegraph system, a lane of traific, a

plurality of transmitters operatively associated with said lane in succession, a sequencing device operable through successive positions individual to each of said transmitters for determining the order of operation of said transmitters, means for preparing an additional transmitter for entrance on to the lane, a control device operable through ing device having an actual position of operation for each of said active transmitters and a potential position of operation for each of said inactive,

transmitters, and means to operate said sequencing device in steps from one active position to the next to determine the order of operation of said transmitters over said lane.

9. In a telegram system, a lane of traffic, a plurality of transmitters certain of which are active and others of which are inactive, a sequencing device having an actual position of operation for each of said active transmitters and a potential position of operation for each of said inactive transmitters, means for changing the potential position of any one of the transmitters on the sequencing device to an actual position thereon, and means to operate said sequencing device in steps from one active position to the next to determine the order of operation of said transmitters over said lane.

10. In a telegraph system, a lane of traffic, a plurality of transmitters certain of which are active and others of which are inactive, a seeration for each of said active transmitters and a potential position of operation for each of said inactive transmitters, means to operate said sequencing device in steps from one active position to the next to determine the order of operation of said transmitters over said lane, a timing device having an actual position for each transmitter, means operable whenever an inactive transmitter is to be rendered active and means acting following the operation of said last means for changing the potential position on the sequencing device of said transmitter to an actual position, whenever the timing device and the sequencing device concurrently attain the positions individual to said entering transmitter.

11. In a. telegraph system, a central station, a plurality of substations, a transmitter at each substation, a single-conductor line circuit connecting each substation to said central station for transmitting from the substation to the central station, a lane of traffic extending from said central station to a remote station, means including said line circuits for transmitting from any of said substations over-said lane of trafilc and means for varying the rate of transmission from said substations over the lane of trafllc in accordance with the number of substations transmitting.

12. In a telegraph system, a transmitting station and a receiving station, a lane of traflic extending between said stations, a plurality of transmitters associated with one of said stations, a recorder individual to each transmitter associated with the other station, means for transmitting telegraph code signals one at a time from any one or more of said transmitters over said lane of trailic, the operating transmitters, irrespective of number, invariably occupying the full lane time and means for recording the signals transmitted from each of said transmitters on its'associated recorder.

13. In a telegraph system, a transmitting station, a receiving station, a lane of traflic extending between said stations, a plurality of transmitters associated with said transmitting station, a recorder individual to each transmitter associated with said receiving station, sequencing devices at the transmitting and receiving stations for determining the number and order of operation of said recorders and means for maintaining said sequencing devices in fixed phase relation.

14. In a telegraph system, a transmitting station, a receiving station, a lane of trafiic extending between said stations, a plurality of transmitters associated with said transmitting station, a recorder individual to each transmitter associated with said receiving station, a sequencing device at the transmitting station for determining the number and order of operation of said transmitters, a sequencing device at the receiving station for determining the number and order of operation of said recorders, means for maintaining said sequencing devices in fixed phase relation, and means for increasing or decreasing the number of transmitters operating over said lane of traffic.

15. In a telegraph system, a transmitting station, a receiving station, a lane of traflic connecting said stations, a plurality of transmitters associating with the transmitting station, a pinrality of recorders associated with the receiving station, means at the transmitting station for entering any of said transmitters for operation over said lane, means for modifying the electrical condition of the lane when a transmitter is so entered and means at the receiving station responsive to said electrical condition for entering a recorder individual to said entering transmitter, the entered transmitters sharing the full capacity of the lane of trafilc.

16. In a telegraph system, a lane of trafiic, a plurality of channels associated with said lane of traffic, each of said channels having sending and receiving or signal devices at opposite ends of thelane of traflic, certain of said channels being idle at times, and means for causing the operating channels to occupy invariably substantially the full capacity of the lane of trafiic, said means including electrical switching means for operatively connecting the channels to the lane of traffic.

1'7. In a telegraph system, a lane of traffic, a plurality of channels, each of said channels having sending and receiving or signal devices at opposite ends of the lane of trafiic, certain of said channels being engaged in the transmission of intelligence and the others not being engaged in the transmission of intelligence, the particular channels which are busy or idle changing according to the trafflc requirements at the moment, and means for causing the operating channels to occupy invariably substantially the full capacity of the lane of trafiic, said means including control means for rendering said channels operative in predetermined order.

18. In a communicating system, a lane of trailic, a plurality of sources of permutation telegraph signals, means for transmitting character signals from all of said sources in succession over said lane of tramc, means for discontinuing the transmission of signals from one of said sources and means for transmitting signals from each of said other sources at more frequent periods.

19. In a communication system, a. lane of traflic, a plurality of sources of permutation telegraph signals, means for transmitting character signals from all of said sources in succession over said lane of traffic, means for starting transmission from an additional source of signals and means for decreasing the frequency of transmission from the other sources of signals to allow time for the transmission of signals from said additional source.

20. In a communication system, a lane of traflic, a plurality of telegraph transmitters, means for rendering said transmitters operative one after the other, means for transmitting at least one whole character signal from each of said transmitters over said lane of trailic before the next transmitter is rendered operative, means for varying the number of transmitters operating over said lane at any time and means for varying the period of transmission from the operating transmitters inversely to the variation in the number of transmitters operating.

21. In a communication system, a lane of traflic, means for transmitting a variable number of messages over said lane of trafiic with the character signals of the various messages intermingled and means for varying the frequency of transmission of the characters .of each message in accordance with the number of messages being transmitted.

22. In a telegraph communication system, a lane of traflic, means for transmitting character signals of a' message over said lane of traiilc with one or more character signals of other messages interspaced between each character signal of said first message, means for varying the number of such interspaced characters and means for varying the frequency of transmission of each character signal of said first message in accordance with the number of such interspaced characters.

23. In a permutation code telegraph system, a transmitting distributor having a contact for each unit of the permutation code, a plurality of transmitters, a line, means for transmittin at least a single character signal at a time, over said contacts to said line from a variable number of said transmitters in predetermined order, a receiving distributor having a contact for each unit of the permutation code, a plurality of receiving instruments and means for distributing over said latter contacts the received character signals originating at each transmitter to a different one of said receiving instruments.

24. In a telegraph system, a plurality of transmitters, a plurality of receivers, each individual to one of said transmitters, a transmitting distributor having a set of contacts common to all of said transmitters, and means for transmitting a single code combination at a time over said common contacts from a variable number of said transmitters to corresponding receivers in predetermined order.

25. In a telegraph system, a transmitting station, a receiving station, a lane of trafilc connecting said stations, a plurality of transmitters associated with the transmitting station, a plurality of recorders associated with the receiving station, said transmitters and recorders being normally unentered on said lane, and means for entering any one or more of said transmitters and a corresponding recorder on to the lane, the entered transmitters operating in succession to transmit characters over the lane to separate ones of said recorders.

26. In a telegraph system, a plurality of transmitters, a synchronous multiplex system, a single channel of said multiplex system common to all of said transmitters, and means for transmitting from a variable number of said transmitters in succession over said single multiplex channel, said means including electrical switching means for operatively connecting the transmitters to said channel.

27. In a telegraph system, a synchronous multiplex system, a plurality of transmitters operable over said multiplex system, means for varying the number of operating transmitters and means for causing the operating transmitters to utilize the same predetermined part of the entire capacity of the multiplex system irrespective of the number of transmitters operating.

28. In a telegraph system a plurality of telegraph transmitters, a storage device, means for transferring a character signal from one of said transmitters at a time to said storage device, a sequencing device for determining the order of transfer of said signals from said transmitters to said storage device, means including the sequencing device for varying the number of transmitters operable into said storage device, a lane of traflic and means for transmitting character signals stored in said storage device over said lane of traflic.

29. In a telegraph system a plurality of telegraph transmitters, a storage device, means for transferring a character signal from one of said transmitters at a time to said storage device, a sequencing device for determining. the order of transfer of said signals from said transmitters to said storage device, means including the sequencing device for varying the number of transmitters operable into said storage device, a lane of trailic, means for transmitting each character signal stored in said storage device over said lane of traflic, a receiving storage device responsive to character signals transmitted over said lane of trafiic to store the same, receiving instruments, means to transfer each character signal from said receiving storage device to one of said receiving instruments and a sequencing device for determining the receiving instrument to respond to each character signal.

30. In a telegraph system, a source of signals representing character signals of a plurality of messages intermingled in predetermined order,

.a plurality of receiving instruments, a storage device common to said receiving instruments, means for storing each character signal in said storage device, means for distributing each character signal stored in said storing device to one of said receiving instruments and a sequencing device for determining the instrument to which each distributed.

31. In a telegraph system, a source or code telegraph signals representing character signals of a plurality of messages intermingled in predetermined order, a receiving distributor having contacts upon which all of said character signals are received, a plurality of receiving instruments associated with said contact and potentially receptive to each received character signal and a character si nal is sequence device for determining the particular receiving instrument upon which each character signal is actually received.

32. In a telegraph system, a lane of traflic over which telegraph signals are received, a plurality of receiving instruments, a sequencing device having an element individual to each receiving instrument, each element serving when selected to condition its associated receiving instrument to respond to character signals received over said lane of traflic, means forselecting said elements in predetermined order and selective means for passing by one or more of said elements without conditioning the associated receiving instrument for operation whereby to .vary the number of receiving instruments responsive in succession to successively received signals, the

frequency of selection of the receiving instruments increasing as the number of active receiving instruments decreases.

33. In a telegraph system, a lane of traific, a plurality of receiving instruments certain of which are active and others of which are inactive, a sequencing device having an actual position of operation for each of said active receivers and a potential position of operation for each of said inactive receivers, said sequencing device operating in steps from one active position to the next to determine the order of operation of said receivers in response to signals received over said lane of trafiic.

34. In a telegraph system, a lane of traffic, a plurality of receiving instruments certain of which are active and others of which are inactive, a sequencing device having an actual p'osition of operation for each of said active receivers and a potential position of operation for each of said inactive receivers and means for changing the potential position of any one of the receiving instruments on the sequencing device to an actual position thereon, said sequencing device operating in steps from one active position to the next to determine the order of operation particular receiving

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