Patent GB-932612-A (GB)
Title: Switching systems between multiplex communication channels
IPC: H04Q11/06
Filed: 1959-10-16
Abstract: 932,612. Automatic exchange systems. STANDARD TELEPHONES & CABLES Ltd. Oct. 16, 1959 [Oct. 21, 1958], No. 35088/59. Class 40 (4). An automatic-exchange comprises a plurality of incoming and outgoing time-division multiplex highways, each carrying pulse code modulated signals, and means for extracting the pulse coded information from one time position on an incoming highway, storing it, and retransmitting it to the appropriate outgoing highway at another time position. The Specification also described arrangements for preventing internal blocking, this feature being claimed in divided Specification 932,613. Signal transfer arrangements between incoming and outgoing highways.-The pulse coded signals are in parallel form so that each highway consists of five conductors for carrying the pulse code elements. Fig. 2 shows one incoming highway El, and ten outgoing highways S1 ... S10. Each pulse position is divided into four equal intervals t1 ... t4 corresponding pulses emitted from the generator GP which also emits a binary coded indication of the pulse position from terminals Co1 Co2, the former being synchronous with t1 and the latter with t2. Two memories M2, M3 store information relative to all calls routed over incoming highway E1. Each row is associated with the pulse position of the call on its outgoing highway. The memory M2 stores the identity of the outgoing highway and the memory M3 stores the time position of the call on the incoming highway E1 Each of these memories has a recording and reading circuit such as EL4 and recording and reading stores such as RE2, RL2 arranged so that the stores are scanned at times t1 by means of inputs Co1 and read out of RL2 at time t3, the recording being reinserted in the store at time t4 unless a different recording is received at t3 by store RE2 in which case the latter is inserted. Store M1 contains a row for each time position on E1 and is arranged to store the P.C.M. signals received on E1 in appropriate time positions under control of the incoming channel store M3. Read out at time t4 is destructive (unlike M2 and M3) and occurs sequentially under the control of time codes applied to Co2. The read out signals are applied to appropriate ones of outgoing highways S1 ... S10 under control of gates P1-1 ... P1-10 opened in appropriate time positions in accordance with the coded outputs from M2 which are translated into single wire outputs by translator SW3. Thus in a call between channel e4 on E1 and channel s14 on highway S2, S2 and e4 are stored on row 14 of M2 and M3 so that in time position 14 the pulses on E1 are stored in row 14 of M1 under control of the output from M3 and these are emitted in time position s14 to gates P1-1 ... P1-10 and the gate P1-2 is opened in this time position under control of M2 to emit the pulses on to S2. Setting up of connection to appropriate highway.-It is assumed that connection is to be established from channel e4 of highway E 1 to audioline LA2-2 which is accessible over highway S2. The control circuit CCO contains the identities E1, e4, S2 and LA2-2 and emits the first three respectively to registers RJE, RTE and RJS whereupon, at the beginning Syn of a pulse repetition period, counter CET is put into position T1. At each time position the identities of outgoing highways using that time position are read out of SW3 to leads 2 for all incoming highway control circuits. Similar identities are emitted from the control circuits of all incoming highways. Translator SW4 is fed from register RJS with the identity of the wanted outgoing highway and enables a corresponding one of gates PE1 ... PE10 to pass pulses busy on this highway to circuit IV which emits a pulse when it does not receive one on its input, i.e. a pulse free on the wanted outgoing highway. This is stored in code form in register RC1. If no storage is effected, i.e. no pulse position is free then at the beginning of the next period, pulse Syn triggers circuit BA1 which informs the control circuit that the connection cannot be set up. Successful storage inhibits the further feeding of free pulse positions thereto. The storage circuit feeds a comparator COM1 which is also fed cyclicly with all the codes so that it emits pulses over lead 3 in the appropriate pulse positions sa to a generator SAG, which emits sa1 ... sa4 lying within the pulse position sa and synchronous with t1 ... t4 respectively. At the same time translator SW5 receives the incoming highway code E1 and operates gates PK1, PG1 to connect up the control circuit for E1 over leads 18, 6. Leads 6 carry codes in any particular time position if any outgoing highway at that instant is in communication with an incoming channel of E1. These codes are fed to a circuit IR which produces an output if it does not receive a code. The first such output has its time position sb stored in code form in RD1. Pulses are subsequently emitted over lead 4 in the time position sb by comparator COM2. These pulses correspond to channels on any of outgoing highways S1 ... S10 which are not in communication with any incoming channel on E1 Pulse sb will be in the time position of the channel on S2 allotted for the connection to E1, e4. It may happen that pulse sb on S2 is at present being used for another connection, e.g. to E8, e5 in which case pulse sa (known to be free on S2) will be used for this latter connection. This may entail further modifications of connections as described later. Pulse sb on lead 4 feeds a generator SBG which produces pulses sb1.... sb4 synchronous with t1 ... t4 respectively. With registers RC1, RD1 full, " and " gate PF1 steps the counter CET to position T2. Counter CE1 is stepped by successive sb1 pulses to emit the identities of all the incoming highways E1 ... E10. At time sb2 the identity of the incoming highway in CE1 is fed into the register R31 and also to translator SW5 which opens gates PK1 to admit the identity of corresponding outgoing highway S2 from the store M2 to the translator/store SW6 which enables the corresponding row of stores SE31 ... SE34 for the rest of the cycle. Translator SW5 also energizes gates PG1 to admit the incoming channel time code e4 from M3 to register R32. At time position sb3 the codes stored in R31, R32 are registered in stores SE31, SE32 on row marked by SW6. At time position sa2 the incoming highway code in CE1 is again applied to translator SW5 and the outgoing highway code received on lead 18 is fed to register R33 and the time position received on lead 6 is received on register R34. At time position sa4 these codes are fed into stores SE33, SE34. This process continues for all positions of counter CE1 provided that the incoming highway is connected to an sb channel of any of S1 ... S10. Thus the stores SE31.... SE34 contain the following information on rows associated with outgoing highways S1 ... S10, (a) SE31, SE32- the identity of the incoming channel (i.e. its highway number and time position) connected to the outgoing channel sb on the outgoing highway concerned; (b) SE33-the outgoing highway (if any) whose sa channel is connected to a channel of the incoming highway registered on SE31, and (c) SE34-the time position of this last channel. Thus, on the row S2 would be registered, say, E8, e5, S1 e11, meaning that S2 sb is connected to E8 e5 and that S1 sa is connected to E8 e11. When counter CE1 finishes its scan it steps counter CET to position T31 and the next sb1 pulse steps CET to position T32. At sb2 the incoming highway code E1 stored in store RJE is applied to translator SW7 which opens the gates PC2, PD2 so that at sb3 the incoming channel code e4 in store RTE is written into the store M3 of E1 and the outgoing highway code S2 in store RJS is written into store M2 of E1 Thus the conditions in the stores for E1 cause the interconnection of E1 e4 with S2 sb. However, this would cause a double connection since as seen above, S2 sb is already connected to E8 e5. This latter connection will now be shifted to S2 sa. At time sb3 mentioned above the outgoing highway code S2 was inserted into temporary store RP1. At time sb4 CET steps to position T33. At the next instant sb1 the registers SE31 ... SE34 under control of the code S2 registered in RP1 reads out the codes in that row to registers R31 ... R34, i.e. these now contain the codes E8, e5, S1 e11. At instant sb2, code E8 is read out of R31 to control translator SW7 to connect up the E8 control circuit. At sb3 codes S1 and e11 in R33 and R34 are fed via leads 13 and 12 to M2 and M3 of the E8 control circuit. At sa2 code E8 from R31 again operates translator SW7 to connect up the E8 control circuit. At sa3, code e5 in R32 is fed to store M3 of E8 and code S2 in RP1 is fed to M2 of E8. Thus the original connections S2sb-E8e5 and S1sa- E8e11 have interchanged their sa, sb pulse positions to become S1sb-E8e11 and S2sa- E8e5. At sa4 code S1 is fed from R33 into temporary store RP1. Thus the double connection referred to above has been removed. However, S1sb may already be connected to another incoming channel, e.g. E5 e4. This connection will be indicated on line 1 of stores SE33, SE34 and operations will proceed as before to effect further interchanges until at least no further displacement of connections is necessary stores SE33, SE34 of the line marked by the code then in RP1 being empty. In these circumstances the code O is read out of the empty store SE33 to store RP1 which thereupon steps CET to T4 and at the next sa4 instant CET is stepped to position RE where all the storage devices in the control circuits are zeroized. Connection of audio circuits to outgoing highways.-Each outgoing highway such as S2 has a store M5 having rows corresponding to pulse positions, each row being capable of storing the coded identity of the audio circuit connected at the moment to the pulse channel, read out being effected at time t3 to a translator SW11 whose outpu