Patent GB-552765-A (GB)
Title: Improvements relating to telephone systems
IPC: F16L59/14
Filed: 1942-01-07
Abstract: 552,765. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., CHRISTIAN, D. A., and DIBBEN, W. H. J. Jan. 7, 1942, No. 252. [Class 40 (iv)] In a satellite system, a local selector, after responding to a discriminating digit, is released completely, the next digit being taken by another selector of the same group. The switch giving access to these selectors may be of the double-hunting type. Circuit arrangements. When the circuit is seized, line and release relays A, B and relays AA, BA and J pull up and the switch JH hunts for a junction under control of KJ. With the arrangement shown in Fig. 1, SH hunts in a similar way under control of KS for a local first selector. Relay A repeats the digits over the junction, to discriminator. magnet DSM and to AA which repeats them to the local selector. JG is operated by the first impulse and locks up. When it is determined that a call is local, LD pulls upon the relapse of dialling relay C, energizes LE and causes the release of KJ and the junction and when it is determined that the call is an outgoing one, JD releases KS and the local selector. Assuming that the first two digits do not determine the destination of the call, DA pulls up after the first and DB after the second, the discriminator proceeding to its next home position in each case and OA pulling up in the second home position and OB in the third. Operation of DA or DB drops KS to start SH in search of another selector. CT, an instant later provides a test circuit for KS until the operation of OA or OB. The circuit provides for metering with the aid of relays MD which pulls up on the called party's reply and V which is released by MD. An operator can hold the connection by holding I to prevent release of BA. The double-hunting switch giving access to local selectors is shown in Fig. 2, the apparatus shown in this Figure replacing that shown in the rectangle in broken lines in Fig. 1. When the circuit is seized; the switch moves off unless it is standing on the terminals of an idle selector. In this case, or when such terminals are reached, TA pulls up if the selector tested by wiper SH3A is idle and TB if only that tested by SH3B is idle. TA energizes KSA and TB KSB to cut the drive. When the destination of the call is not determined at the end of a digit, DA or DB drops KSA or KSB. The test relay TA or TB is momentarily shunted by ground from the releasing selector ahead but if the other selector available in this position is idle, the other test relay pulls up to initiate its seizure and prevent the switch from driving off. Otherwise the switch hunts as before. If it reaches the second half of its bank, OF is energized and locks up so that on reaching contact 12 for the second time the switch is stopped. If all the junctions are busy, the switch JH stops in an overflow position, supervisory relay I is not energized and, if relay JD is operated, an overflow meter is operated and busy tone goes back.. If the switch SH fails to find a local selector there is no circuit for operating I if LO is operated and the relapse of JG, which follows that of KJ, connects up the busy tone.