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US3558830A
(en)
|
|
Overvoltage transmission line protector
|
|
US3867588A
(en)
|
|
Quick disconnect for telecommunication lines
|
|
US3582562A
(en)
|
|
Key telephone intercommunication system
|
|
US4171469A
(en)
|
|
Abbreviated dialing system
|
|
US4459435A
(en)
|
|
Telephone privacy apparatus
|
|
US3660609A
(en)
|
|
Subscriber long line extender
|
|
US3689705A
(en)
|
|
System for party line signalling using re-encoded ringing signals
|
|
US3843844A
(en)
|
|
Subscriber loop circuit apparatus
|
|
US2293869A
(en)
|
|
Signaling system
|
|
US4262172A
(en)
|
|
Ring-trip detector
|
|
US4209667A
(en)
|
|
Subscriber drop-connected circuits
|
|
US3865995A
(en)
|
|
Universal subscriber{3 s line circuit in a key telephone system
|
|
US3471651A
(en)
|
|
Telephone ringing circuit
|
|
US3626101A
(en)
|
|
Loop extender for subscribers connected to a central office by abnormally long telephone lines
|
|
US2055647A
(en)
|
|
Telephone line system
|
|
US2924667A
(en)
|
|
Reduction of transmission loss in bridged subscriber loops
|
|
PL62296B1
(enrdf_load_stackoverflow)
|
|
|
|
US3689700A
(en)
|
|
Subscriber loop extension unit
|
|
US3730999A
(en)
|
|
Telephone ring-trip circuit
|
|
SE8703890D0
(sv)
|
|
Anordning vid inkoppling och urkoppling av en ringsignal till en uppringd abonnet
|
|
GB1563130A
(en)
|
|
Switching circuits
|
|
US4199659A
(en)
|
|
Electronic prepay adapter circuit for central office telephone equipment
|
|
US4145579A
(en)
|
|
Key telephone unit protective coupler
|
|
CA1144671A
(en)
|
|
Central office interface circuit
|
|
US3662116A
(en)
|
|
Subscriber superimposed signaling unit
|