|
US2556103A
|
|
Switching arrangement for combined manual and automatic telephone systems
|
|
GB557680A
|
|
Static frequency reducers
|
|
GB555011A
|
|
Improvements in electrical control systems
|
|
US2324659A
|
|
Telephone system
|
|
US2322650A
|
|
Impulsing apparatus for signaling systems
|
|
US2311214A
|
|
Telephone system
|
|
US2314990A
|
|
Telephone system
|
|
US2329022A
|
|
Call transmitter
|
|
US2326457A
|
|
Alternating current signaling system
|
|
US2298910A
|
|
Automatic switch
|
|
US2315010A
|
|
Signaling system
|
|
US2299660A
|
|
Automatic telephone system
|
|
US2308752A
|
|
Thermionic valve circuit having a constant output
|
|
US2320549A
|
|
Telephone system
|
|
US2297068A
|
|
Signaling system
|
|
US2320548A
|
|
Telephone system
|
|
IE16241L
|
|
Party line systems.
|
|
IE16407L
|
|
Telephone exchange networks.
|
|
US2294863A
|
|
Electrical storage and delay circuits
|
|
US2305178A
|
|
Current supply system
|
