Patent GB-240320-A (GB)
Title: Improvements relating to automatic and semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-11-12
Abstract: 240,320. Siemens Bros. & Co., Ltd., and Patterson, W. G. Nov. 12, 1924. Addition to 205,651. Automatic exchange systems.-The selector of the parent Specification, which is enabled to hunt through several levels by the operation of a separate rotary release magnet at the end of an unsuccessful hunt over a level, is modified to allow rotary release to take place at an early position of a busy level. The invention is described with reference to connectors with separate release detents, as described in Specification 136,497, serving ordinary lines and private branch exchange groups occupying two or more levels, and provided with means, as in the parent Specification, for preventing hunting if a P.B.X. line other than the first in a level is dialled: In the connector shown in Fig. 1, in which rotary release may take place on the first terminals of a level, the extra terminals of grouped lines in all the levels but the last (with the exception of the last terminal in each level, which is left dead) are connected to wires r, s, and over a bridging wiper S which partakes of vertical movement only, to the relay PS which controls rotary release. The final level is connected to a wire t. The wires r, s, t are grounded over contacts o1, e, Fig. 3, of idle line switches, and relay PS is thus short-circuited. If the last level is busy, there is no ground to energize the hunting controlling relay PR and busy tone is sent back from the first terminals, which are thus not distinguished from ordinary lines. In the system shown in Fig. 2, in which rotary release may take place on the 2nd of the grouped terminals in a level, the extra terminals except the last, in the final level, are permanently grounded, and if this level is busy the wipers move to the last terminals before sending the busy signal. In the other levels, the first terminal is permanently grounded, and the others, except the last, are connected to wires r, s, as in the system shown in Fig. 1. There is no vertical wiper, relay PS being connected to the wires r, s over a contact of the relay PR which pulls up over the permanent ground at the beginning of each level. Except as regards rotary release, both connectors operate in the same way, and the two paragraphs following can be read with either Figure. Connection to ordinary lines. Line relay A energizes release relay B and the tens digit operates the vertical magnet VM in a. circuit a1, C(1), g1. The change over of vertical springs k<2> and the relapse of series relav C energize relay G to transfer the impulse circuit to rotary magnet RM. Rotary springs w1, w2 change over, and the relapse of relay C connects up the test relay Hand unlocks relay G. If the line is busy, relay H fails to pull up, relay G falls back energizing relay C(2) and removing a short-circuit from relay F(1) which sends back busy tone over BS, c1, f5. If the line is idle, relay H pulls up, holds up relay -G, and completes the ringing circuit over winding 2 of relay F. When the called party replies, relay F locks up by removing a short-circuit from its winding 1, lights lamp LP, and extends the loop to the back-bridge relay D, which releases relay G and puts out LP. Release is under control of relay A, which releases relay B to energize the main release magnet MM and to release relays H, F, D. Connection to an idle P.B.X. line in the first level. When relay C falls back after the wipers have been brought to the first line of a P.B.X. group, relay PR pulls up over X‹, g6, c5. If this line is idle and relay H therefore pulls up the line is rung as in the case of ordinary lines. If relay H fails to operate, relay G is held in a circuit c2, g2, pr2, w1, k2, and the rotary magnet RM operates in a circuit g1, pr4, h6, pr3. At the end of the stroke, contact rm1 short-circuits relay PR which opens the rotary circuit, and re-energizes immediately. If this line is busy the rotary circuit is remade. This interaction continues until relay H opens the rotary circuit permanently, whereupon the line is rung. Rotary release if a level is busy, Fig. 1. The absence of ground from the wire r allows relay PS(1) to pull up in series with relay PR when relay C falls back at the end of the units digit. Relay PS locks up over its winding 2 in series with relay PT and short-circuits relay PR to release relay G, which re-energizes relay C(2). The latter energizes the rotary release magnet MM1 over c5, ps2, C(1), g3, w1, k2. The restoration of rotary springs w1, releases relay PS and winding 2 of relay C but relay PT remains locked up. The relapse of relay PS short-circuits relay C(1) and energizes vertical magnet VM over g1, ps5, pt3, pt2. This circuit is transferred by relay G, when relay C falls back, to the rotary magnet RM. The change over of rotary springs w<2> unlocks relay PT to open the rotary circuit, and hunting proceeds as in the first level. Relay PS operates to cause rotary release whenever the level becomes busy during a hunt. In case, however, all the lines ahead of the wipers become busy and a line already passed over becomes idle, the wipers move to the last terminals of which the extra terminal is dead. and a busy signal is sent as with an ordinary line. Rotary release, Fig. 2. The permanent ground at the beginning of each level energizes relay PR and short-circuits relay PS whether the level is busy or idle, and the wipers move to the second set of terminals if the first line is busy. If the level is busy, relay PS pulls up over pr5, PR, g<6>, c5, pr5 'being arranged to hold on after pr1 has fallen back on the operation of the contact rm1. Rotary release now takes place as described in connection with Fig. 1. Metering systems. Back bridge reversing relav D connects up booster battery BB over g5 and releases the sluggish (change-over) relay G, which replaces BB by a ground connection.