Continuous monitoring in carrier telephone systems
AssigneeCarrier Telephone Corporation of America, Inc.
InventorSidney Browne
Life of this patent
Estimating the term…
Abstract
A continuous monitoring arrangement for a carrier telephone system utilizes the subscriber carrier at a reduced level when the subscriber set is on-hook. Proper reception of the reduced carrier level at the central office circuit during on-hook condition verifies operability of the carrier frequency circuitry. In a preferred embodiment the central office carrier, which is always present, is modulated by a control tone in the audio range during on-hook conditions. The control tone is detected at the subscriber circuit and modulates the reduced level subscriber carrier whereby reception of the control tone back at the central office circuit verifies operability of all carrier and voice frequency circuits at both subscriber and central office locations.
Claims9
In a carrier telephone system of the type in which information is transmitted from a remote station to a local station as modulation of a first carrier frequency signal and information is transmitted from said local station to said remote station via a second carrier frequency signal, and in which there exists idle and busy operating modes, an arrangement for continuously monitoring operabiity of said system comprising:
- means for transmitting said first carrier signal at a relatively high level during said busy mode and at a relatively low level during said idle mode;
- means at said local station for detecting reception at said first carrier signal at said relatively low level;
- means at said local station for detecting reception of said first carrier signal at said relatively high level;
- and
- indicator means at said local station for providing a failure indication in the absence of reception of said first carrier signal at at least said relatively low level.
In a telephone carrier system of the type in which plural remote subscriber stations each communicate with a respective one of plural central office terminals using different carrier frequencies via a common transmission line;
- each subscriber station including:
- a receive section for receiving a specific central office carrier frequency signal modulated by voice frequency signals from a respective central office terminal and separating the voice frequencies therefrom, and a transmit section for modulating a specific subscriber carrier frequency signal with voice frequency signals and transmitting the modulated subscriber carrier to a respective central office terminal via said common transmission line;
- each central office terminal including:
- a receiver section for receiving a specific subscriber carrier frequency signal modulated by voice frequency signals from a respective subscriber station via said common transmission line and separating the voice frequencies therefrom, and a transmit section for modulating a specific central office carrier with voice frequency signals and transmitting the modulated central office carrier to a respective subscriber station via said common transmission line;
- an arrangement for continuously monitoring operability of said system comprising:
- at each subscriber station:
- means for distinguishing between when the subscriber station is in an idle on-hook mode and a busy off-hook mode;
- means for selectively attenuating the transmitted subscriber carrier to a relatively low level in response to a on-hook mode at said subscriber station, said relatively low level being significantly lower than the normal subscriber carrier level during said off-hook mode;
- at each central office terminal:
- low level detector means for detecting reception of the attenuated subscriber carrier during said on-hook mode;
- and
- indicator means for providing a fault indication in the absence of reception of said attenuated subscriber carrier during said on-hook mode.
The method of continuously monitoring the operability of individual channels of a multiple channel carrier telephone system of the type in which multiple remote subscriber stations communicate with respective local central office terminals via a common transmission line using different subscriber and central office carrier signal frequencies for each channel, said method comprising the steps of:
- at each subscriber station:
- transmitting the subscriber carrier signal at a normal level during a busy off-hook mode and at a substantially reduced level during a idle on-hook mode;
- at each central office terminal:
- detecting reception of said subscriber carrier at least at said substantially reduced level during said on-hook mode;
- and
- providing a fault indication in the absence of detected subscriber carrier at a level at least equal to said substantially reduced level.
Dependencies are inferred from the claim text.