GB1401128A - 4-wire telecommunication networks - Google Patents

Abstract

1401128 Automatic exchange systems SIEMENS-ALBIS AG STANDARD TELEPHON UND RADIO AG and HASLER AG 23 Feb 1973 [29 Feb 1972] 8956/73 Heading H4K In a centrally controlled network, 4-wire connections between a calling switching point and a called switching point are tested by a testing device in such a manner that a digital signal sent out from the testing device to the calling switching point is looped back to the testing device for comparison with a reference signal. The connection between the testing device and the called switching point is then likewise tested and the connection between switching points is completed. The network shown comprises a number of switching points S1-S5, Sk-Sn (defined as points where transmission channels of a first group may be connected to transmission channels of a second group, e.g. line concentrators, multipliers &c.), and a number of exchange points V 1 -V 5 (defined as points where each transmission channel may be connected to any other transmission channel), which are interconnected by 4-wire connections which may be T.D.M. highways. Some of the exchange points, e.g. V 3 , V 4 , V 5 , include registers WE 1-3 having associated therewith testing devices P1-P3, which in the case of T.D.M. transmission can test a number of connections simultaneously on a time sharing basis. It is also indicated that for all idle 4-wire connections a loop exists between the two directions of transmission at each switching point and exchange point. In setting up a connection, control ST first establishes a connection between a calling switching point, e.g. Sk, and a register WE2, but the loop between transmission directions is maintained at the calling switching point Sk. A testing device P2 then sends out a digital signal to the calling switching point Sk where it is looped back to the testing device, for comparison with a reference signal. Assuming an acceptable connection, a second test is performed by removing the loop at the calling switching point and checking that no signal is then received back. Assuming the check is positive, the register WE2 transmits a proceed to send signal and information from switching point Sk relating to the called switching point, e.g. Sn, is received in the register WE2. Control ST then establishes a 4-wire connection between the register WE2 and the ca led switching point Sn via exchange points V 4 , V 1 , V 5 , and switching points S 5 (indicated in heavy lines in Fig. 2, not shown). This 4-wire connection is then tested from testing device P2 as above and the connection is switched through to give a 4-wire connection from Sk to Sn via S1, S2, V3, V1, V5, S5 (indicated in heavy lines in Fig. 3, not shown) the connection to the register in exchange point V4 being dropped. A false loop connection can be investigated by successively looping the 4-wire connection at points progressively nearer to the testing device until one of the connections tests correctly.