Patent GB-724520-A (GB)
Title: Improvements in or relating to electronic time division multiplex switches
Inventor: SCOWEN FRANK
IPC: H04J3/04
Filed: 1951-11-06
Abstract: 724,520. Automatic exchange systems. POSTMASTER GENERAL. Feb. 20, 1953 [Nov. 6, 1951], No. 26009/51. Class 40 (4). A number of circuits B11 . . . 13, 21 ... 23 capable of being selectively connected to a circuit S1 of a plurality of such circuits, are divided into two (or more) groups each group being associated over synchronous pulse multiplexes M1, M2 with individual highways H1, H2 respectively, the selective equipment associated with each circuit S1 comprising means S11, S12 for associating the circuit S1 with either of the highways H1, H2. In one embodiment, Fig. 3, each group has an associated marker multiplex MM1, MM2 synchronous with M1, M2 to whose respective inlets MB 11 . . . 13, 21 ... 23 markings may be applied to generate on the respective marking highways MH1, MH2 marking pulses coincident with the pulse positions of their associated circuits in M1, M2. Assuming lead MB23 is marked then the resulting pulses on MH2 are applied to a pulse lengthener L2 whose output operates a bistable trigger T2 which disables a corresponding trigger T1 to prevent any marking pulses over MH1 from being effective at this time. Trigger T2 also opens the gate G2 to admit the pulses on MH2 to the master selector SEL1 (which may be of the type described in Specification 722,179). If the selector receives more than one pulse train from MH2 it selects one, say that due to MB23, and indicates it on a lead indicative of that train. Such indicating leads are fed in common to a number of " slave " selectors one of which is associated with each outlet S1. Each slave selector consists of, a plurality of triggers TS1 ... TS5 enabled over a marking lead MK associated with the outlet S1, and the first three triggers are connected to the master selector SEL1. The trigger TS3 in the marked slave selector is thus operated to open a gate G13 which admits the pulse p3 to the lead C. The trigger T2 indicative of the wanted group operates the marked trigger TS5 in the slave and the output thereof places group marking potential on lead B. Thus with the gate S12 opened over lead B, and the modulator/demodulator SMD1 pulsed by pulses p3, connection is established between circuit B23 and circuit S1. The pulses on lead C are gated by G15 (operated by TS5) to the pulse suppression gate PSG2 which prevents further pulses in this pulse position on MH2 from seizing another circuit such as S1. The operation of TS5 causes the unit D to produce a restoring pulse for the trigger T2 and the master selector SEL1. Release may be effected by the application in known manner of a restoring pulse over lead REL to the triggers TS1 . . . 5. If a circuit in group B11 . . . 13 had been marked triggers T1 and TS4 would have operated to mark lead A to open gate S11. In a second embodiment, Fig. 4, the six marker leads are all applied to a single multiplex MM3 having six pulse positions which may be independent of those of M1 and M2. A marking pulse or lead MH3 is selected by a master selector SEL2 and indicated by a combination of two leads, one from a group of three leads (leading to TS1 . . . 3) and one from a group of two leads (leading to TS4, TS5) as described in Specification 722,179. Triggers TS4, TS5 in the marked " slave " selector put enabling potential on leads A, B respectively for their appropriate gates, and triggers TS1 . . . TS3 admit to lead C over gates such as G11 appropriately timed pulses p1 . . . p3 respectively. Triggers TS1 ... TS5 also open gates G111 . . . G115 which pass " three-phase " pulse trains P<1>/1 . . . p<3>/1, and "two-phase " pulse trains P<1>/2, p<2>/2 of the type described in Specification 722,179 to gate G116 to determine the pulse position of the pulse accepted by the selector SEL2, this pulse being then fed to the suppression gate PSG3 for reasons described above. Restoration of the master selector and release takes place as previously described.