437,646. Multiplex telegraphy. WESTERN UNION TELEGRAPH CO., 60, Hudson Street, New York, U.S.A.-(Assignees of Holcomb, P.) April 4, 1934, No. 10227. Convention date, April 13, 1933. [Class 40 (iii)] Comprises an expanding-channel system wherein a lane of communication such as one channel of a multiplex system or a telegraph circuit or radio channel is fully occupied by one or more members of a group of startstop transmitters sending characters in turn, the number of instruments using the lane being variable under manual or automatic control. Time-entry automatic expanding-channel system, Fig. 2. The line L1 is fed by a transmitting distributer TD1, one five-segment channel of which is allotted to three transmitters, Ta, Tb, Tc. When all three are supplied with tape they take turns to send a character through the brush B9, so that each transmitter uses the lane constituted bv the five-segment channel once for every three revolutions of the brush. If one transmitter such as Ta closes down automatically on exhausting its tape, the remaining two share the lane between them, occupying it during alternate revolutions of the brush : similarly the channel may be flexibly shared between any number of transmitters associated with it. So long as all three transmitters are in action their turns are allotted to them by brush B10 crossing segment 46. If the turn of transmitter Ta has arrived, segment 46, besides causing the restoring-windings 48 to reset the transmitting-contacts 200, sends a pulse via armature 73a to earth through winding 75 and segment a of the mixer TM1. Thus armature 75a causes the tape magnet SM to release momentarily so that the tape contacts 201 are set according to a code signal, which is stored in contacts 200. Winding 41 is thereupon energized through one or more of the contacts 201 and resets the armature 75a and tape magnet SM, which restores contacts 201 to their spacing position and feeds the tape one step. Meanwhile the impulse from segment 46 has also energized magnet 69 so as to allow the brush of the mixer TM1 to move on to the next segment and thus to allot the next turn to transmitter Tb. Before this turn arrives, the signal stored as described above on contacts 200 is sent on by brush B10. Closing down a transmitter and receiver, Fig. 2. If the tape of transmitter Ta becomes exhausted it opens contact 49 immediately after the tape-feed movement caused by segment 46. It therefore unbalances relay DR and, via earthed contact 52, locks the magnet SM so as to withdraw the tape pins continuously. Thus when segment 46 is next reached an all-spacing signal is sent to line ; and when segment 47 is reached immediately afterwards, an impulse is sent via contact 75a (which is still to the left owing to interruption of the restoring-circuit at 201) to winding 62 so that battery + is applied at 67 to segment a of the mixer TM1 ; hence at every subsequent revolution the release magnet 69 acts as soon as the wiper reaches segment a, and the brush passes at once to segment b, giving that turn to transmitter Tb. The pulse from segment 47 which has thus put Ta out of action passed through windings 63 and 64 which neutralized one another, but immediately after the occurrence of this pulse the condenser 70 discharges and restores contact 75a to the right. At the receiver, the relays SB store the signals for printers Pa, Pb, Pc, which operate in turn under the control of mixer RM1, whose brush B11 moves on by one segment every time the segment 97 of the distributer RD1 is crossed by brush B12. The operating magnet 89 of the printer whose turn has arrived is energized at the same time. When the closing-out signal (00000) is received for printer Pa, the coded contacts of relays CB apply battery via lead 93 to segment a2 of distributer RM1 so that brush B11, on reaching that segment, causes winding 89 to set its armature 89a to the right, connecting battery continuously to segment a1 so that thereafter the mixer RM1 passes over the turn of transmitter Ta without pausing. Re-entry of a transmitter and receiver, Fig. 2. When the transmitter Ta is again ready to send, the tape-controlled contact 49 closes, so as to prepare the re-entry of Ta into the system, but the actual moment of re-entry is determined by the sending-clock SC. The wiper of this clock is released by magnet 71 so as to move on by one segment every time the brush B10 crosses segment 46. Thus the mixer TM1 does not keep step with it when a transmitter Ta has been closed down. When the brush reaches segment a<1> it energizes winding 55 via contact 56 (which was set to the left when the closing- down impulse passed through winding 62) and via contact 53, which has now been released as a result of the action of the tape. Winding 55 locks up and prepares at 79 a circuit such that when the brush B9 reaches the segment a<11>, relay 73 operates so that the next impulse from segment 46 passes via conductor 82 instead of 74 and sets up a re-entry signal (000+0) on the contacts 200. Whatever the position of the brush B8 of mixer TM1 at this moment, the mixer pauses for one cycle because the impulse from segment 46 has been diverted at 73 so as not to reach the escapement magnet 69 ; but this impulse effects restoration of the parts so as to leave transmitter Ta ready to act when the brush B8 reaches segment a. Meanwhile the receiving clock RC is stepped forward by magnet 99 at each impulse coming from segment 97, so that the clock keeps step with that, SC, at the sending station though not with the receiving mixer RM1. At the receiver a re-entry signal (000+0) is received from transmitter Ta when the brush B14 is on segment a3. This signal causes the coded contacts CB to energize winding 95 so that the succeeding impulse from segment 97 is diverted through brush B14 and segment a3 of the clock to winding 91, which restores the circuit of relay 87. Meanwhile the mixer RM1 pauses for one cycle, the impulse from segment 97 having been diverted away from magnet 96. Thus the mixers RM1, TM1, take in the channel Ta, Pa, without losing step with one another. Manually controlled system. The operations of closing-down and re-entry may be carried out by means of manually operated switches, Fig. 1 (not shown), instead of the clocks SC and RC. Time-and-turn-entry system, Figs. 3, 4, and 5. In this system a station which has been closed down cannot re-enter until the sending clock and transmitting mixer have come into step. When all three transmitters X, Y, Z, Fig. 3, are using one channel of the main distributer MD, Fig. 4, and when brush B21 is pausing on segment x of transmitting mixer TM2 so as to give this turn to transmitter X, brush B19 sends an impulse through segment 125 to magnet 155 so as to move the mixer brush B21 through one step, the circuit passing through winding Mx which acts to short-circuit the line resistance 118 and so operates marginal relay MRx, Fig. 3, which starts the distributer Dx of transmitter X by energizing magnet M. An impulse from segment 109 operates the tape-setting magnet SM, and a signal from transmitter X is sent over the distributer Dx and distributer D<1>x, Fig. 4, to relays PTR which send it on over the main distributer MD to line ML. At the receiving end, Fig. 5, signals pass through the main receiving distributer MRD to polar relays PRR and thence in multiple to distributers TDx, TDy (which feed branch stations or printers) and printer MPz which prints locally the messages from transmitter Z. Whenever brush B23 passes over segment 163 of distributer MRD, an impulse passes via. conductor 166 through one or other of the magnets 171, 179, 195 which set the sending-on distributers and printer in action, and through the appropriate segment of mixer RM2 to magnet 177, which releases the mixer brush B26 for one step. The sending clock SC, Fig. 4, and receiving clock RC1, Fig. 5, keep step with one another under the control of impulses from segments 125 and 163 respectively. Closing down a transmitter and receiver, Figs. 3, 4 and 5. When contact 116, Fig. 3, of transmitter X is broken owing to shortage of tape, relay CRx releases so as to unbalance the differential relay DR ; hence on receipt of an impulse from segment 109, relay DR locks up and locks the stepping magnet SM of the transmitter so that an all-spacing signal is continuously applied to the tape contacts Tx. A closing-down signal (00000) is thus sent to relays Rx, Fig. 4, and earth is applied by them over lead 121 to winding 122 of relay Lx which energizes relay Kx. Battery is thus continuously applied to segment x of mixer TM2, through armatures of relays Kx, Ky and Kz in series, and the turn of transmitter X is consequently passed over thereafter. At the same time a closing-down signal (00000) is sent on by relays PTR over line ML and received by relays PCR, the coded contacts of which apply battery via lead 182 to relav COx whose contact 183 shortcircuits the release magnet 171 so that the start-stop distributer TDx ceases to function. When segment 163 is reached by brush B23, the brush B26 of mixer RM2 is released and on passing over segment x2 this brush energizes winding 185 via contact 184 which has now been closed. Winding 185 locks up and applies battery continuously to segment x1 so that this segment thereafter loses its turn. The contacts of relays Kx, Ky, Kz, Fig. 4, are so arranged that if all three stations close down, brush B21 stops at each turn on segment x of mixer TM2. Re-entry of transmitter and receiver, Figs. 3, 4 and 5. When contacts 116, Fig. 3, of the closed-down transmitter X are closed again by the action of the tape, relay CRx releases, applying earth at contact 113 to the line RLx, since contacts RBx were all closed by the closing-down signal (00000). Resistance Rx is thus short - circuited, and marginal relay Jx, Fig. 4, is consequently energized through one or other of its windings. This relay applies earth to w