Patent GB-231260-A (GB)
Title: Improvements in or relating to automatic or semi-automatic telephone systems
IPC: H04Q3/00
Filed: 1924-01-14
Abstract: 231,260. Automatic Telephone Manufacturing Co., Ltd., and Ostline, J. E. Jan. 4, 1924. Automatic and semi-autoautomatic exchange systems.-Relates to connectors serving Private Branch Exchange groups, and arranged to hunt only when the first line of a group is dialled, acting as an ordinary connector for all other lines. The connectors have an auxiliary test wiper and bank, the auxiliary terminals corresponding to the first line of a group being connected to battery, and those corresponding to the other lines of a group being connected to the corresponding regular test terminals. The auxiliary terminals corresponding to last lines and individual lines are left dead. Hunting is controlled by a relay connected to both wipers, and which therefore is energized only if the connector stops on a first line. The bank terminals are connected to a terminal block, Figs. 2 and 4, at which the necessary connections between the regular and auxiliary test terminals are made. In one of the two embodiments described the change-over relay functions also as the stepping relay, and a busy signal is given by connecting ground and battery alternately to a talking wire so as to give a flash signal to an operator as well as by sending tone current. Another feature concerns a relay which is made slow to release by energizing weakly a second winding, the holding current being insufficient to keep it permanently operated. First arrangement, Figs. 1 and 2. Line relay 4 and release relay 5 are energized in the usual manner and the tens digit is repeated to vertical magnet 15. The relapse of series relay 6 transiers the impulse circuit to rotary magnet 16 and the upper winding of relay 11 in parallel for the units digit. Relay 11 completes a circuit over its lower winding to make itself slow to release. If the wipers come to rest on a busy line, busy relay 10 pulls up, and if the line is the first of a P.B.X. group, the relapse of relay 11 shortly afterwards, energizes, over both test wipers, relay 8 which locks up and energizes the stepping relay 12. Relay 12 completes a holding circuit for relay 8 independent of relay 11 and energizes the rotary magnet 16 and relay 11. If the next line is busy, relay 8 remains energized over the (grounded) auxiliary terminal 76 after it is unlocked when relay 12 is released by magnet 16. The relapse of magnet 16 therefore re-energizes relay 12 to cause a further step. This inter-action continues until an idle line is found or until the last line of the group is reached. In either case the auxiliary wiper fails to find ground and the relapse of the stepping relay releases relay 8 which disconnects the stepping relay. Busy signal. If the last line or a. called line other than the first of a group is busy, relay 10 locks up when relay 11 falls back and busy tone is connected to the lower talking wire. Supply of ringing current. If after hunting or directly in response to dialling, the wipers stop on an idle line, relay 10 falls back or fails to energize and, when relay 11 falls back a little later, switching relay 9 pulls up sluggishly in series with the called cut-off relay, locks itself, and sends out ringing current over ringing-cut-off relay 7. When the called party replies relay 7 pulls up, locks, and energizes the back-bridge reversing-rela,y 3. Second arrangement. Change-over relay used as stepping relay. Line relay 104 and release relay 105 operate as usual and the tens impulses are repeated to vertical magnet 115 and changeover relay 106 in parallel. Relay 106 short-circuits its upper winding to make it slow to release. The relapse of relay 106 after the tens digit switches over the impulse circuit to rotary magnet 116 which responds to the final digit. Relay 111, which is energized in parallel with the rotary magnet, short-circuits its upper winding to make itself slow to release. The connector now operates as in the first arrangement, relays 107 - - 111 corresponding respectively to relays 7 - - 11. but the place of relay 12 is taken by relay 106, the upper winding of which is kept permanently open by relay 108. It will be noted also that in this arrangement the lower test wiper is the normal one. Busy signal. When busy tone is to be sent, and accordingly relay 110 locks up when relay 111 falls back, the short-circuit normally across resistance r is removed and the busy wire B.F.T. is connected through it to the lead. In addition to supplying the usual tone currents, the wire B.F.T. is connected alternately to battery and ground to give a flash signal in case the connection was made through an operator. According to one Provisional Specification, relay 8, Fig. 1. energizes in two steps, partially from a local ground over the auxiliary test wiper to connect the stepping relay to the regular test wiper, and fully if the stepping relay pulls up. On full energization the relay disconnects its original circuit and locks in a circuit dependent on the stepping relay and the auxiliary test wiper. According to the other Provisional Specification, a group selector may be provided with a relay for use both as a change-over and as a stepping relay.