Patent GB-191213963-A (GB)
Title: Improvements in Intercommunicating Telephone Systems.
IPC: H04M9/00
Filed: 1912-06-15
Granted: 1913-05-01
Abstract: 13,963. Automatic Telephone Manuf a c t u r i n g Co., A i t k e n , W., Cooper, H., and R e m i n g t o n, C. June 15. I n t e r c o m m u n ication s y s t e m s ; exchange systems.-Intercommunication systems are provided at each station with a relay which is energized to disconnect the telephone instruments if the station called is already busy. A switch of the kind described in Specification 22,983 / 11 is used, and a call is made by depressing the arms a, a<1> of the switch on to the studs of the line wanted, and actuating the ringing key b. A calling circuit is made from the battery n over contacts 3, 2 of a key b, arm a<1>, contact 2<a>, line p, contacts 3, 4 of the switch-hook d<1>, and bell e<1>, back to the battery. A talking circuit between stations A and B is made from the receiver f and microphone h at the station A, contacts 2, 6 of the switch V, arm a, contact 2, line p<1>, microphone h<1> and receiver f<1>, contacts 3, 4 of the relay t<1>, contacts 1, 3 of the switch-hook d<1>, line p, arm a<1>, contacts 2, 1 of the key b, contacts 2, 1 of the switchhook d, contacts 4, 3 of the relay t, and contacts 5, 1 of the switch V back to receiver f. Current is fed to this line over the inductance g<1> at the called station. If station B is busy when the station A calls, the contact between springs 5, 6 of switch C completes a circuit from battery n over relay t, contacts 6, 5, arm a<1>, contact 2<a>, line p, contacts 3, 2 of the switch-hook d<1>, contacts 2, 1 of the key b<1>, and contacts 2, 4 of the switch C<1> back to the battery. The armature of the relay t completes a hold-on circuit for itself independent of contacts 6, 5, thus permanently breaking the circuit of the telephone instruments at the station A for this connexion. A call from the exchange C is received on the bell w and the operator at the station A switches in his instruments by closing the contacts 1, 3 and 2, 4 of the switch V. If another station on the system is required by the exchange, the contacts 7, 11 are closed to bridge the exchange line by the coil g<2>. If the station B is wanted, the operator there moves his switch to the contacts x, x<a>, thus completing a circuit from the battery n<1> over contacts 8, 12 of the switch V, lower winding and contacts 1, 2 of the relay u line q, arm a<3>, contacts 2, 1 of the key b<1>, contacts 2, 1 of the switch-hook d<1>, contacts 4, 3 of the relay t<1>, the telephone instruments, arm a<2>, line ql back to battery n<1>. The relay u completes a permanent circuit for itself from the exchange battery over its contacts 2, 3 and 5, 7, and gives the flag signal 6. The return of the telephone instruments to the switch-hook at the station A restores the switch V. A call from a station as B to the exchange C is made in the same way by moving the switch to contacts x, x<a>, thus energizing the relay u. If the exchange line is busy, the relay t<1> is energized over a circuit from battery n through relay t<1>, contacts 6, 5 of the switch c<1>, arm a<3>, line q, and contacts 3, 2 of the relay u to earth at the exchange C.