Patent GB-205651-A (GB)
Abstract: 205,651. Siemens Bros. & Co., Ltd., and Christian, D. A. Sept. 15, 1922. Automatic exchange systems comprise selectors arranged so that at the end of an unsuccessful hunt over one level, the selector is released as regards its rotary motion by a rotary release magnet and is given a vertical step, and proceeds to hunt over the next level. In the drawings, relays enclosed in rectangles are slow-release relays. Fig. 1 shows a connector for ordinary lines and lines to a private branch exchange, of the type described in Specification 136,497 but having in addition a release magnet M<1> for rotary movement only, two slow-release relays PS, PT, and an extra wiper comprising arms 10, 11 co-operating with a terminal bank 12. The latter consists of a metal half-cylinder connected to ground and having terminals screwed into it for all P.B.X. lines except the last. The extra wiper controls a relay PR for controlling the hunting. Connections to ordinary lines. When the connector is seized relays N, A operate and energize relay D which prepares a circuit for the vertical magnet H. Magnet H operates in response to impulses and at the end of the digit relay D falls back, off-normal contact K<3> having been shifted, and energizes relay G which switches over the impulse circuit to the rotary magnet R and reenergizes relay D. Relay D completes the impulse circuit and a holding circuit for relay G. Magnet R operates in response to impulses and at the end of the digit relay D falls back, completes the test circuit and de-energizes relay G, the rotary offnormal contact W<1> having now been opened. If the called line is idle, relay T operates in the interval between the relapse of relays D, G, locks up over its low-resistance winding 2 and de-energizes relay A which removes a short-circuit from ringing relay S and allows it to operate when relay G falls back, and connect ringing current from wires 13, 14 to the called line. Reply of the called subscriber energizes relay TR which locks up by opening a short-circuit across its holding winding 2 and short-circuits relay S which completes the talking circuit. When the calling station hangs up relay N falls back and de-energizes relay T so that the connection is released. If the called line is busy, relay T does not operate when the line is tested so that relay A does not fall back. The relapse of relay G energizes relay TR over its second winding and busy tone from the leads 15, 16 is connected to the calling station. Connections to P.B.X. lines. If the called line is busy but is the first line of a P.B.X. group, relay PR is energized over ground at terminal bank 12, completes a holding circuit for relay G, and connects the interrupter 15<a> to the rotary magnet R. Hunting proceeds until the wipers reach an idle line when relay T energizes and releases relay PR, and ringing proceeds as before. If the wiper C finds all the grouped lines in that level busy, it passes on to the next contact which is connected to relay PS. Relays T, PS energize in series. Relay PR falls back, opens the rotary magnet circuit and releases-relay G, which energizes relay PT over the second winding of relay PS and the rotary off-normal contact w<2>. Relay PT releases relays A, T, the latter completing a circuit for the rotary release magnet M<1>. The wipers accordingly return to normal as far as rotary movement is concerned and off-normal contact w<2> changes over, breaking the circuit of relays PS, PT, and completing a new one for relay PT. Relay D energizes over rotary off-normal contact w<1> and energizes the vertical magnet H over back contacts of relays A, G and the wipers are lifted to the next level. By this time relay PS falls back, de-energizing relay D which energizes relay G. Relay G prepares the rotary magnet circuit and re-energizes relay D which completes it and the wipers receive one rotary step and open the circuit of relay D at contact w<1>. Relay G also opens the circuit of relay PT which falls back slowly and re-energizes relay A, and the latter opens the rotary magnet circuit and connects it to front contact p<r2>. If the line is idle, ringing proceeds as before, but if busy relay PR operates and hunting proceeds. The extra wiper is provided with the trailing arm 10 so that if a P.B.X. line, other than the first in a level, is called relay PR is short-circuited and the wipers do not hunt. Group selector. Fig. 2 shows the invention applied to a group selector. Relay A pulls up when the selector is seized and energizes relay D which connects the vertical magnet H to the impulse circuit. At the end of the digit relay D falls back and connects the rotary magnet R in a circuit including an interrupter and a contact of the test magnet T. When relay T energizes, on the wipers reaching an idle line. it locks up over its winding 1, stops the hunting, grounds the cwiper, extends the a and b wires and releases relay A which disconnects the winding 2 of the test relay from the c-wire. If there are no idle lines in the level, the wipers move to 11th terminals. The windings 2 of relays T, PS energize in series. Relay T locks itself to the c-wire over its winding 1 under control of relay PT, de-energizes the rotary magnet and relay A. Relay PS locks up over its winding 1 in series with relay PT. Relay PT pulls up and releases relay T which energizes the rotary release magnet M<1>. The wipers return to their normal rotary position and rotary offnormal contacts w<1>, w<2> change over and energize relay D which locks up under control of relay A, energizes the vertical magnet H and breaks the circuit through relays PS, PT. The wipers receive a vertical step and relays PS, PT fall back slowly. Relay PS energizes relay A which releases relay D and the interrupter circuit is again completed for the rotary magnet. All the levels over which hunting is required except the last have 11th cterminals connected to relay PS. The 11th c-terminal of the last level may be connected direct to battery so that when the wipers reach it relay T energizes and busy tone connected to the 11th a and b terminals is sent to the calling station. Specification 136,497 is referred to.