Patent GB-190610599-A (GB)
Title: Improvements relating to Telephone Exchange Systems.
Filed: 1906-05-05
Granted: 1907-05-04
Abstract: 10,599. Lake, H. H., [Stromberg-Carlson Telephone Manufacturing Co.]. May 5. Telephone systems; telephone calls.-Relates to the supply and control of ringing-current injunctionline working between a main and a sub-exchange, the operator of the sub-exchange controlling the application of ringing-current to the called subscriber connected to the main exchange, and the supply of ringing-current continuing until the called subscriber replies, when it is automatically cut off. The invention is described as applied to a system in which the called subscriber is on a party-line, a selective call being obtained by the use of currents of different frequencies. The selective ringing-mechanism for the main exchange is similar to that described in Specification No. 10,580, A.D. 1906, in which a depressed ringing- key is automatically locked in its depressed position by a locking-relay, the circuit of which is broken when the called subscriber answers, thus releasing the depressed key. The sub-exchange operator's control of the application of ringing-current is effected by means of a relay 48, bridging the junction-cord circuit T, and energized to complete the ringing-circuit when the said operator depresses the ringing-key K to connect in the generator G. The calling sub-station A is of the local battery and magneto call type. In response to the actuation of the call annunciator 7, the operator at L inserts the answering-plug 8, and ascertains the connexion desired. This connexion is communicated through the usual order circuit (not shown), to the main-exchange operator at M, who then inserts the calling-plug 27 into the required jack, depresses'the required party-line ringing-key 54<1>, and notifies the operator at L which junction line to use. The insertion of the calling-plug 27 completes a circuit through the cut-off relay 25, and the relay 46, the attraction of the armature 52 completing a circuit through the wires 93, 84, armature 70, and supervisory lamp 53. The insertion of the plug 9 into the junction-line jack 30 completes two circuits-(a) from the battery 21, through the wire 81, relay 41, wire 87, contact 51, wire 88, and extra plug contact 15 to ground ; (b) from the battery 21, through the wire 81, relay 57. and wire 88, to ground as before. The relay 57 locks the depressed key 54<1>, and attracts its armatures 56, 58, thus extending the ringing-circuit from the generator 61<1> to the contacts 74, 75, which at this stage are disconnected from the armatures of the relay 41, this relay having been energized as described. The operator at L then depresses the ringing-key K, bridging the alternating generator G across the cord circuit. The current flows over the junction lines and through the condenser 49, and relay 48, which attracts its armature 50, thus completing a maintaining-circuit through the winding 79 and contact 80. The attraction of the armature breaks the contact 51, thus de-energizing the relay 41, the armatures of which then complete the ringing-circuit from the generator 61<1>, through the interrupter 63', contact 68, key 54', condenser 59, contacts 58, 72, wire 90, contacts 74, 43, contacts 45, 44, tip of plug, sub-station apparatus, plugsleeve, contacts 40, 75, contacts 73, 56, key 54', and thence back to the generator. Periodical supply of ringing-current then continues until the called subscriber removes his receiver, thereby completing a circuit from the battery 21, through the relay 46, plug sleeve, sub-station apparatus, plug tip, contacts 44, 45, 43, 74, 72, 58, relay 76, key 54<1>, contact 68, segment 66 of the interrupter 63', wire 69, and contacts 71, 52 to the battery. The relay 76 is unresponsive to the ringing-current, but responds to this direct current, opening the contact 77, 78 in the circuit of the maintaining-winding 79 of the relay 48, which is thus de-energized and releases its armature 50 to close the contact 51 in the circuit of the relay 41 as before. The relay 41 then attracts its armatures, breaking the ringing-circuit and completing the talking-circuit. The segment 66 of each interrupter 63<1> is connected to the ring 64, which is grounded through the wires 69, 84, and the contacts 71, 52. There are thus alternate applications of ringing-current and ground to the called subscriber's line, so that the line is relieved of static charges after each application of ringing-current. The arrangement of the supervisory apparatus is as follows :-When the plug 9 is inserted in the jack 30, but before the station B<1> has replied, the supervisory relay 17 is included in the following circuit :-from the battery 21 to the armature 94 of relay 95, winding 32 of the repeating-coil 34, sleeve strands of the junction and cord circuits, relay 17, tip strands of the cord and junction circuits, repeating-winding 31, and armature 98 to the battery. The relay 17 is thus energized and the lamp 19 is lighted until the called subscriber removes his receiver, thereby completing a circuit from ground through the relay 95, wire 99, contacts 42, 43, contacts 45, 44, tip of plug, substation apparatus, plug sleeve, and relay 46 to the earthed battery 21. The energizing of relay 95 breaks the circuit of the supervisory relay 17, thus notifying the operator L that the called subscriber has answered. When the conversation is finished, the subscriber hangs up his receiver, thus breaking the circuit of relay 95, so that relay 17 is again energized, giving the clearing-out signal, whereupon the operator at L withdraws the plugs 8, 9. Withdrawal of the plug 9 breaks the circuit of the locking relay, the de-energizing of which releases the depressed ringing-key 54<1>, and again completes the circuit of the supervisory lamp 53, thus giving the clearing-out signal to the operator at M.