Patent GB-1246382-A (GB)
Title: Circuit arrangement for subscriber's number translator in telecommunication exchanges, particularly telephone exchanges
IPC: H04Q3/545
Filed: 1969-01-22
Abstract: 1,246,382. Automatic exchange systems. TELEFUNKEN PATENTVERWERTUNGS G.m.b.H. .22 Jan., 1969 [23 Jan., 1968], No. 3669/69. Heading H4K. In a directory/equipment number translator having a main store, the storage area allotted to each directory number address contains, in addition to the corresponding equipment number, an indication of the class-of-service and of the free/busy state of the line together with an alternative directory number address which may be accessed if the considered line is busy; During a translation all the data is transferred to a buffer store where it is updated if necessary before being rewritten in the main store. The alternative address may be in respect of a group of PBX lines or an emergency service. The class of service may be incoming or outgoing trunks barred. Particular description. Calling line.-Data from each storage area in turn of a main ferrite core store SB is read-out into buffer store SR under the control of an address register AR. The binary coded hundreds, tens and units digits of each equipment number POS are then used to interrogate the line circuits TS identified thereby and the results of the interrogation are returned to the common circuitry via gates G1 . . . GN only one of which is opened in dependence on the thousands digit of the equipment number POS. If a formerly free line is found to be busy, the word KTS is set to zero by logic L1 and central control ZST is informed that the line is calling together with its class of service KA via logic L2. The stepping of address register AR is inhibited until ZST has completed its control function in respect of the line. If a formerly busy line is found to be free, the word KTS is incremented by 1 bit, the data in SR is rewritten into SB and the address register is incremented so as to provide a next directory number for addressing SB. The word KTS continues to be incremented on each appearance of the directory number until it reaches a predetermined value whereupon central control is informed that it must break down the connection in respect of this line, the address register being inhibited during this process. In the event of permanent loop conditions, the combined busy mark from the line circuit TS and the free mark from the c wire prevent the word KTS from being incremented to its free value whereby central control's time is not periodically wasted on setting-up a connection which, due to a lack of dialled digits, is broken down within a short period. Called line.-When all the digits pertaining thereto are stored in a register R, they are transferred to address register AR via Q1 and are there used to address the main store SB in place of the normal output of the address register. The cabled line is interrogated as before and if it is free central control is informed accordingly. The word KTS is updated and, after a pause to allow ZST to complete the connection, the stepping of AR is recommenced. However, if the called line is busy, an instruction bit B may be effective to cause ZST to transfer the contents of alternative directory number location SF via Q2 to the address register whereupon the process is repeated in respect of the alternative number. If this process is unsuccessful and if no further alternative numbers are available, central control reverts busy tone to the caller.