Patent GB-768683-A (GB)
Title: Improvements in or relating to electric circuit arrangements for supplying trains ofelectric pulses
IPC: H04Q11/04
Filed: 1953-12-04
Abstract: 768,683. Automatic exchange systems. GENERAL ELECTRIC CO., Ltd., and BEESLEY, J. H. Nov. 24, 1954 [Dec. 4, 1953], No. 33772/53. Class 40 (4). A time-interlaced pulse train is generated at a selected one of a plurality of output terminals, the arrangement comprising a plurality of gate devices with said output terminals, said gate devices being connected to a combination of fewer delay devices in such manner that application of a control pulse causes pulses to circulate through said delay devices. The invention is applied to a 100-channel multiplex automatic telephone system serving 500 subscribers' line terminating units and 10 pairs of trunk terminating units, the channels by which speech and other signals are transmitted being in the form of 100 time-interlaced trains of ¢ Ásec. pulses. Gate devices 91-9500, Fig. 1, are connected in different combinations to 3 out of 16 delay lines L1-L16 so as to form circulating delay circuits. Control apparatus causes a ¢ Ásec. pulse corresponding to the phase of a free channel to appear at input terminal 104 of the gate device, say G1, corresponding to the line terminating unit of a calling subscriber. This pulse appears at output terminal 103 and in each of branch leads o1, o2, o3. The resulting pulses are delayed by 100 Ásecs. in delay lines L1, L2, L3 and appear simultaneously at the inputs of 3-gate 101 to establish circulation. Output terminal 103 therefore feeds a train of ¢ Ásec. pulses spaced by 100 Ásec. intervals to a modulator/demodulator in the subscriber's line terminating unit. Circulation is stopped when the control circuit applies a pulse of the same phase to inhibiting terminal 105. The delay lines may be of mercury or magnetostrictive type. Leads k1-k16 are preferably coaxial cables. Modifications. The gate devices may be connected to delay devices arranged in 2 or 3 separate groups (Figs. 2 and 3, not shown). Fig. 9 shows the arrangements of Figs. 1-3 in more schematic form with additional features. A gate device Gxyz is connected to a combination of delay lines Lx, Ly, Lz. Each output lead of a delay line includes a 1-gate such as gx<SP>11</SP>1 with alternative means for starting circulation. A called subscriber can be identified by a combination of 3 input terminals Tx, Ty, Tz and the channel by the phase of a control pulse applied to these terminals. Circulation can be stopped by alternatively an inhibiting pulse applied to terminal 106. Partial protection against simultaneous calls. In the systems so far described, two subscribers calling simultaneously may be allotted the same channel. This risk is reduced in the systems of Fig. 10. Terminals Tv1-Tv16 and' Tw1-Tw16 apply 100 Ásec. pulses cyclically every 1600-1700 Ásecs. to corresponding 2-gates gv1-gv16 and gw1-gw16 which also receive ¢ Ásec. free-channel control pulses so that only two leads in the group m1-m16 receive pulses at the same time. To set up circulation in gate device G1, a control voltage is applied to terminal 104. At some time subsequently control pulses appear simultaneously on leads i2, i3 and the 3-gate 101<SP>11</SP> starts circulation and delivers an output pulse to terminal 103. The output at 103 is arranged to remove the control voltage from 104. The number of subscribers who can be allotted the same channel is reduced from 500 to 14. By arranging the delay lines in groups, this number can be further reduced (Figs. 11, 12, not shown). The system is also shown more schematically in Fig. 18 with the addition of 1-gates in the outputs of the delay lines. Pulse circulation may be started by the application of simultaneous pulses of the right phase to terminals Tx, Ty, Tz and pulse circulation may be stopped by the application of a pulse of the right phase to terminal 106. Complete protection against simultaneous calls being allotted the same free-channel control pulse is provided by the system shown in Fig. 19. The system is generally similar to those of Figs. 10-18 but the inputs to the first group C of delay lines differ. When ¢ Ásec. pulses appear on any two or more of leads kc0-kc4, gate 109 responds to inhibit gates gk0-gk4 to prevent circulation. Pulse circulation may be stopped at gate 109<SP>1</SP> by the application of an inhibiting pulse to an additional input (not shown) while pulse circulation may be started at terminals Tx, Ty, Tz, Fig. 22. In the system just described, if two or more parties call simultaneously no party is allotted a channel. This difficulty is overcome in Fig. 27. Terminals TX, TY, TZ are associated individually with delay lines Lx, Ly, Lz and receive 100 Ásec. pulses cyclically every 500, 1100 and 1300 Ásecs., respectively. Freechannel control pulses are fed from terminal 108 to 2-gates gx, gy, gz. Pulse circulation is set up by applying a control voltage to terminal 104. Gate gkxl passes a pulse to delay line Lx, however, only if a control pulse from terminal 108 is simultaneously passed to the other input of gate gkx<SP>1</SP>. This can happen only at the coincidence of pulses on terminals TX, TY, TZ, i.e. at a time unique to the calling line. When an output appears at 103 the control voltage at 104 disappears, but if there is no signal at terminal TX the condition for the suppression of the voltage at 104 does not persist and the control voltage reappears. Pulse circulation may be stopped by an inhibiting pulse at terminal 106. Pulse circulation may be started at gates gx, gy, gz, the details being omitted for clarity. Economising on coaxial cables. The number of input leads, and therefore coaxial cables, is reduced to five in Fig. 31. The 3-gate 101a in the gate device has a single lead to the associated delay line in the group Lx, the leads to this group being all connected to a 1-gate 110 which feeds two groups of 2-gates such as gky, gkz feeding appropriate delay lines Ly, Lz. When control voltage is applied to terminal 104, gate device Gxyz responds to free-channel pulses applied to terminal 108. Gate device Gxyz feeds a pulse to delay line Lx and 2-gates such as gky, gkz, but only those 2-gates which receive free-channel pulses from 108 via gy<SP>1</SP>, gz<SP>1</SP> transmit the pulse to the corresponding delay lines. Inhibiting pulses may be applied to gate 110 (Figs. 32, 33, 36, not shown). Starting and stopping may be effected at gates in the outputs of the delay lines (Figs. 34, 35, 36, not shown). Whereas Figs. 31-36 give only partial protection against two gate devices being allotted the same free-channel pulse, full protection is given in Fig. 37 in which two gate devices pulsing simultaneously energize gate 109 to inhibit gate 1101. Reduction of input leads to one. In Fig. 39 each output lead from a gate device Gxyz is connected to a common lead k feeding the delay lines through 2-gates gkx<SP>1</SP>, gky, gkz. The 2- gates admit pulses to the respective delay lines when such pulses occur simultaneously at respective additional outputs of gates such as gy<SP>1</SP>, gz<SP>1</SP> and on common lead k. Fig. 41 (not shown), has an input lead for each delay line in the first group as in Fig. 31. Trunk terminating units. For trunk terminating units there is no need to start pulse circulation at the gate devices which are accordingly reduced to a 3-gate each, Fig. 42, pulse circulation being started at terminals Tx, Ty, Tz. Pulse inhibition may be effected at terminal 105 or at 1-gates gx, gy, gz (Fig. 43, not shown). Abolition of input leads. In Fig. 47, the leads from the gate devices to the delay lines are abolished. Pulse circulation is set up by applying control pulses to a combination of terminals such as Tx, Ty, Tz. The delay lines are in a closed circuit and cause gates gx<SP>1</SP>, gy<SP>1</SP>, gzl to pulse leads mx, my, mz and so produce a pulse at terminal 103.