Telecommunications – Receiver or analog modulated signal frequency converter – Signal selection based on frequency
Patent
1978-12-04
1980-07-15
Robinson, Thomas A.
Telecommunications
Receiver or analog modulated signal frequency converter
Signal selection based on frequency
179 251, 455 9, H04J 112, H04B 116
Patent
active
042130158
ABSTRACT:
A power failure alarm circuit for a transmission line communications system such as a telephone system having means for transmitting and receiving carrier signals connected to a trunk line at an end central office. The alarm circuit monitors the power level of a selected number of the different frequency carriers received on the trunk line and generates an alarm condition signal when the combined power levels fall below a predetermined magnitude. The carrier signal receiving means responds to the alarm condition signal to release the subscribers. After a predetermined delay, the alarm circuit generates an alarm busy signal and the receiving means responds by forcing the trunk lines busy to prevent seizure by new callers. The alarm circuit also monitors the level of power being sent to signal repeaters connected to the trunk line and generates an enable signal when said power is lost. The transmitting means responds to the enable signal by pulsing the carrier signals to signal another end central office of the alarm condition.
REFERENCES:
patent: 3135951 (1964-06-01), Byrne
patent: 3895187 (1975-07-01), Antoszewski
patent: 4015206 (1977-03-01), Huntley
patent: 4087639 (1978-05-01), Beene et al.
Clemens William J.
Reliance Telecommunication Electronics Company
Rickin Michael M.
Robinson Thomas A.
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