Patent GB-414503-A (GB)
Title: Improvements relating to automatic telephone and like selective systems
IPC: H04Q3/42
Filed: 1933-06-27
Abstract: 414,503. Automatic exchange systems. SIEMENS BROS. & CO., Ltd., Tothill Street, London, LONG, D. P., 3, Ingleby Way, Chislohurst, Kent, and PATTERSON, W. G., 59, Grove Park Road, Mottingham, London. June 27, 1933, No. 18276. [Class 40 (iv).] A single-motion selector having staggered pairs of wipers which come into engagement with corresponding arcs of terminals in turn has two home positions in which one or other wiper of each pair stands at the beginning of its arc, and the selector upon release advances to the nearer home position, while upon seizure it may advance from one home position to the other in order to decrease the hunting time in response to a preliminary digit or discriminating signal. The invention is described with reference to an incoming group selector having two sets of staggered pairs of wipers and controlled by a digit switch which receives first a digit which determines whether a preliminary movement of the selector is necessary, and then marks the group to be searched in response to a second digit, the position of the digit switch also controlling the operation of the relay which connects up one or other set of wipers. Normal operation. When the selector is taken into use, relay WS(i) energizes over the incoming junction and connects up relay H which reverses the connections to WS(i), thus sending back a signal to hold up impulse transmission in the register-controller at a preceding exchange. Earth is connected to the start wire st to operate relay ST in the common control circuit. One control circuit normally serves each shelf of selectors, and relay GP is operative when the control circuit is free. When however, the control circuit is taken into use, the start wire st is extended over chain contacts gpl to a free control circuit allotted to another shelf of selectors. The switch CF rotates to associate the control circuit with the seized selector, when relay TB energizes in series with K and connects up TC. Relay K transfers the junction wires to line relay A, WS and H being disconnected, thus sending back a signal to restart impulse transmission. Relays B(i), C(i) energize, connecting up SG and releasing GP. The switch DS takes the first digit which determines whether the arcs of terminals W, Y or X, Z are to be used, relay PQ(i) or PP(i) being energized over wiper ds7 when series relay C(ii) falls back. Relay SG falls back in turn and causes the advance of the switch DS to its subnormal position 11, in which C(i) re-energizes over wiper ds3 followed by SG and HU. The latter closes a circuit for the latch magnet LM of the selector. If the wipers are standing at the beginning of the arcs W, Y or X, Z in which selection is to be made, relay T energizes immediately over contact pq2 (operated or not) and wipers 10, 14 and opens the latch magnet circuit. If however the wipers are not standing at the beginning of the appropriate arcs, they are advanced through 180‹ to that position, whereupon T energizes and stops the selector. In response to the second digit, the switch DS is arranged to take two steps for each impulse or for each impulse after the first by means of a self-stepping circuit over alternate terminals of wiper ds2, contact pp2 (operated or not) and A(iii). The switch has 25 positions, and in order to provide 20 marking positions beyond its subnormal position, it is adapted to be stepped a second time if necessary over its earlier positions. At the end of the digit C(ii) falls back and disconnects SG, while the opposing relay winding PP(ii) or PQ(ii) is connected up to release that relay. Relay T falls back and the latch magnet LM re-operates, allowing the selector to hunt for an idle outlet in the group marked over wiper ds4. When this is found, T re-energizes followed by G and TA and the latter connects up switching relay H. A discriminating signal may be sent forward when required over terminal 02 and wiper ds6. The relapse of line relay A initiates the release of the control circuit. If the wanted group is connected to the arcs of the lower set of wipers, wiper-switching relay WS operates over terminal O and wiper ds5. A group may be connected partly to early positions in the arcs Y, Z and partly to late positions in the arcs W, X. In this case WS operates over terminal 01 and wiper ds5 under the control of SG which holds up long enough for the first part of the group to be searched and then falls back and releases WS. Upon release, H falls back and connects up the latch magnet LM, so that the selector advances to the nearer home position, the off-normal contacts on being arranged to change over in both home positions. Busy and dead-number arrangements. If all the outlets of the marked group are busy, the selector rotates to the last position of the arc, whereupon T energizes in series with LC(i) and the opposing relay winding TA(ii) which prevents the operation of that relay. Relay LC applies busy tone and flash from wire BT, and actuates an overflow meter over wiper ds8. If the first digit received does not correspond to the outlet groups available, LC(ii) energizes over terminal 04 and wiper ds8 in series with SG, and number unobtainable tone is applied from wire NU. If the second digit represents a spare group, no marking is applied and LC(i) operates as in the case of a busy condition, and in addition, SG reoperates over terminal 03 and wiper ds5, so that NU tone is applied. Supervisory arrangements. While the switch CF is in motion, relay RA(ii) energizes and the lamp SL is flashed. When the switch CF stops the slow flash is changed to a rapid flicker until start relay ST falls back, after which the lamp glows steadily. The lamp SL is also flashed or caused to glow steadily by RA(i) when the switch DS operates. Relay RB controls the lamp SSL according to the condition of the selector. If the control circuit is held for an excessive time, relay S(i), ST(ii) are operated by time pulses over wires SS, ZZ and the lamp SL flickers. The Provisional Specification refers to Specification 388,173.