Patent GB-1031431-A (GB)
Title: Improvements in or relating to time-division multiplex communication systems
IPC: H04Q11/04
Filed: 1963-03-04
Abstract: 1,031,431. Automatic exchange systems. SIEMENS & HALSKE A.G. March 4, 1963 [March 2, 1962], No. 8489/63. Heading H4K. In a system in which connections are set up under control of a recurring series of pulses, each connection being allocated a particular pulse phase, and in which presence of a pulse in a memory associated with a line indicates the busy condition of the line, the memories are tested in turn by a generator emitting the identities of the lines, and if the subscriber belongs to a PBX group the generator emits a further signal which inhibits the emission of busy tone which would otherwise be sent if the line tests busy. As shown, Fig. 2, lines are interconnected by pulsing two gates such as SN1, SN2x simultaneously to connect them to the multiplex highway SM, the pulses being received from stores Ua, Ub in which the identities of the calling and called lines are stored in the pulse phase allocated to the connection. Normal call.-When a line initiates a call a free pulse position (one of positions P1.. P94 in a cycle of 100 such positions) say P1, is allocated to the call and inserted in store Uda and also in a combination of stores in Ua indicates the identity of the calling line and a free register MM is allotted to the call. When the wanted subscriber's directory number is received by the register it transfers it to the store Ub in phase P1. Counter AZ emits line equipment numbers in turn to comparators AA, AB and also to UM which issues the corresponding directory number over A1. When this number corresponds with that registered in Ub comparator P.B emits a pulse over r/vb at phase P1 and this 's inserted in store UGTn, Fig. 3, and also brings up E1 During phases P1... P95 comparison is also made by AA, AB between the equipment number emitted from AZ and equipment numbers stored in Ua, Ub. If the line is busy a pulse output occurs at one of these phases over a/va or a/vb to bring up A/VA or A/VB. This closes gate K22 and opens K17 to bring up EB thereby allowing the pulse stored in UGTn to be passed via bs<SP>1</SP> to store Ubz whence it operates gate SB to connect busy tone to the multiplex highway SM. If the line is free however, K17 is closed and K22 opens to bring up EF. This permits the stored pulse to pass over vb<SP>1</SP> to store Udb and to gate DS<SP>1</SP> to permit the equipment number stored in AZ (whose stepping has been arrested by means not shown) to be passed in the appropriate phase to Ub. Insertion of this address deletes the previous number stored at this phase. The pulse on vb<SP>1</SP> is also inserted in Urz, Ufz to initiate the sending of ringing current and ringing tone from Rz and Fz. The called line is thus connected to the speech multiplex at the same phase as the calling line. Call to PBX line.-Assuming the PBX directory number is dialled, then when AZ reaches the equipment number of one of the PBX lines then UM also emits a signal over lead s and this inhibits gate K18 thereby preventing EB from operating so that no busy tone is reverted. AZ continues stepping until the equipment number of another of the PBX lines is reached when tests are again carried out as before. Each time one of the lines, say of group S1 tests busy counter K32 is stepped. When the last line of the group tests busy K32 and the busy signal on bss open K64 to set K1. With a PBX group signal on s K43 now opens, followed by K18 to set the busy trigger EB to cause busy tone to be reverted as described above. Call to a particular line of the PBX group.- Such a line if it can be called individually (e.g. as for night serivice) is allocated a distinctive directory number. When AZ reaches the equipment number of this line UM is caused to emit this distinctive number over A5 (as well as the normal directory number over Al). This is compared with the number stored in Ub in a comparator RBS to provide an output over rs/vb. This in conjunction with the signal r emitted from UM opens gate K27 which brings up E1 and E<SP>1</SP>1. Busy testing takes place as before, but the E<SP>1</SP>1 output inhibits the s mark at gate K43, thereby permitting K18 to open and operate the busy trigger EB. In a modification not using the special comparator RBS it may be arranged, e.g. for night service, that at this time the circuit UM emits over A1 the special directory number instead of the PBX ordinary directory number. A call to this number can then be set up in the ordinary way.