Patent GB-190414523-A (GB)
Title: Telephone Systems.
Inventor: FAIRWEATHER WALLACE
Filed: 1904-06-28
Granted: 1904-11-10
Abstract: 14,523. Fairweather, W., [American Electric Telephone Co.]. June 28. Telephone systems; telephone c a l l s. - Relates to centralbattery telephone exchange systems, and comprises among other features the automatic short-circuiting of the subscriber's line at the time of making the call, in order to prevent the production of disagreeable sounds in the receiver when the call is answered. In the system shown in Fig. 1, local batteries 56 are used for the substation transmitters Tr, and each substation is provided with a generator M and bell 14. A condenser 2 is placed in one arm of the line near the jack. When a call is sent by actuating the generator M, the current passes at the exchange through the line relay R, lamp L, and battery B to earth, returning from earth at 9 to line through the armature 11 of the cut-off relay R'. The armature r of the relay R shortcircuits the subscriber's line at 17, 18, thereby closing the circuit of the battery B through the lamp L and relay R. The lamp consequently remains alight until the cut-off relay breaks its circuit at the points 4, 10 and connects the line to the spring jack. This is effected when the call is answered, the insertion of the answering plug P into the jack J serving to make contact at 22, 23 and to close an earth circuit of the battery B through the cut-off relay R'. By pressing the listening key K, the operator's speaking set 26, 41a is connected to line, and the number of the subscriber to be called is ascertained. The calling plug P' is then inserted in the proper jack J', thereby closing the contact 22, 23 and energizing the relay R<1> so as to connect the line with the jack. The ringing-key K<1> is pressed and the subscriber called up, the speaking circuit being completed when he lifts the receiver from the book. The clearing-out drop I is actuated by either or both of the subscribers ringing off at their generators after returning their receivers to the hooks. The magnetos at the substations may be dispensed with, and the bell grounded, ringing- current from the exchange being transmitted through one side of the line and earth. The condenser 2 is in this case omitted, and the line relay energized by the current which flows in the line when the receiver is lifted from the hook, the call being thus made automatically. The clearing- lamp relay is energized when either receiver is returned to the hook, by current flowing through one side of the line and through the bell to earth. The battery at the substation may be used to give the clearing-signal through the line. The lamp L may be located in the circuit connection 18. In the arrangement shown in Fig. 6, two batteries are used at the exchange, the battery B being used for signalling and the battery B' for speaking and for operating the supervisory signal lamps L', L<2>. Short-circuiting of the line is not provided for. The call is given by lifting the receiver from the hook, thus energizing the relay R and closing a local circuit through the lamp L. The cut-off relay R<1> is energized by current flowing from the battery B<1> through the impedance coil a, supervisory lamp L', sleeve 29, and the test ring 30, with earth return. While either subscriber's receiver is off the hook, his supervisory lamp is extinguished, being shunted at r' through the action of the line current passing through the repeating-coils c, h and relay R<2>. Listening and ringing keys K, K' are associated with the cord circuit as shown.