Patent GB-392280-A (GB)
Title: Improvements relating to automatic telephone systems
IPC: H04Q3/42
Filed: 1932-01-13
Abstract: 392,280. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Caxton House, Tothill Street, PATTERSON, W. G., 68, Eltham Road, Lee, both in London, and LONG, D. P., 3, Ingleby Way, Chislehurst, Kent. Jan. 13, 1932, No. 1045. [Class 40 (iv).] A single-motion final selector adapted for P.B.X. hunting is controlled numerically by a digit switch which marks directly individual lines, first lines of P.B.X. groups and night service lines, while lines of P.B.X. groups other than the first are marked by a switch which takes up one or more positions in succession in accordance with markings applied by the digit switch. A large group is thus divided into a number of sub-groups which are searched successively, and in response to different digits, the search may be restricted to one or more sub-groups, or the sub-groups may be searched in a different order. The selector has two sets of wipers which, in one embodiment, are connected up alternatively by a discriminating signal from the previous selecting stage, the marking arrangements for P.B.X. lines being modified accordingly. In the second embodiment, all numbered lines appear in one bank and wiper-switching is controlled by the switch which marks P.B.X. lines. The digit switch and marking switch are common to a group of final selectors, and the selector and the marking switch are of the motor-driven type described in Specification 388,173. First arrangement, Fig. 1 ; impulse reception. Upon seizure, line relay A(i) energizes over a loop circuit in series with relay P(i) or over the negative wire to ground and connects up release and dialling relays B(i), C(i), the latter in series with relay JB, which removes shortcircuits from the associating relays such as K(i) of the selectors of the group. Relay K(i) energizes and locks over K(ii), while relay P(i) if operated locks over P(ii) and connects up wiper-switching relay WS(i) which locks over WS(ii). Impulses are repeated at contact a<1> to the magnet DSM and dialling relay C(ii), to advance the digit switch, which takes two steps for each impulse of the tens digit due to a self-interrupting circuit over the odd terminals of the bank DS1. On the relapse of relay C, one or two of relays W, X, Y energize over wiper DS2 and connect up the appropriate one of marking wipers DS4..8. Relay E energizes and the digit switch advances to the subnormal position 11 or, if that position has already been passed, to the normal position. Relay C reoperates and connects up relay F, which opens the circuit over the odd terminals of bank DS1, so that the digit switch advances one step for each impulse of the units digits. When relay C falls back, the latch magnet LMM operates and starts the marking switch MS rotating. ' Call to an individual line. In this case' the digit switch applies no marking to banks MS6, 7 and the switch MS rotates to its last position, in which relays TX, TY pull up and lock over wiper MS8 in series with relay LD, stopping the switch MS and connecting up the latch magnet LMS of the selector, which rotates into engagement with the line marked by the digit switch over contact ty2 and test relay T. If the line is idle, this relay operates, stopping the selector and connecting up relay TT, whereupon relay E falls back and switching relay H energizes, grounding the d wire to initiate ringing from a preceding feed bridge circuit, as described in Specification 378,585. If the wanted line is busy, relay T does not operate and the selector rotates to its last position, in which relay LC operates in series with relay T and sends back a busy signal. Call to a P.B.X. The digit switch marks one or more positions in the bank MS6 or 7, and the switch MS stops in the first of these positions due to the operation of relays TX, TY, which lock independently of relay LD and start the selector. Jumper connections are made only to the odd terminals of bank MS6 and to the even terminals of bank MS7, the bank to be effective being determined by relay P. Six lines of the P.B.X. group are now marked, the first over the digit switch and the remaining five over wipers MS1 .. 5. If all these are busy the selector rotates to its last position in which relay LC operates and restarts the switch MS. The selector steps to normal on the relapse of relays TX, TY. The switch MS stops in a second position marked by the digit switch and marks a further set of five lines of the P.B.X. group, over which the selector searches as before. If all the lines of the group are found busy, the switch MS rotates to its last position in which relay LD operates, and the selector again steps to its last position to operate relay LC to give a busy signal. It is evident that the lines of a group may occupy any positions in the selector banks, and by dialling different digits the search may be restricted to one of more sub-groups, or the order of the sub-groups may be varied, different sets of positions being marked in the bank MS6 or 7 by the digit switch. A call to a night service line is set up like a call to an individual subscriber, no marking being applied to banks MS6, 7. Second arrangement, Fig. 2 (not shown). All individual lines, first lines of P.B.X. groups and night service lines are reached over one set of wipers of the final selector, while the other set of wipers gives access only to unnumbered P.B.X. lines. Stopping positions for the switch MS are marked only in bank MS6, while bank MS7 is employed to effect wiper-switching in the selector when the switch MS is set to a position in which unnumbered P.B.X. lines are marked, there being no discriminating relay P. The operations are otherwise similar to those of the first arrangement.