Telephone station carrier system
OwnerSidney Browneinventor
Life of this patent
Estimating the term…
Abstract
A station carrier telephone system employing single sideband transmission permits optimal utilization of the available frequency spectrum without requiring individual stable subscriber carrier sources by utilizing a common source signal for all subscriber carriers. The common source signal is received via the common transmission line at each subscriber circuit where it is processed and mixed with the similarly received central office carrier to derive a difference frequency signal which serves as the subscriber carrier. In a preferred embodiment sixteen channels share the common transmission line and employ sixteen adjacent subscriber frequency bands and sixteen adjacent central office frequency bands.
Claims22
In a frequency-multiplexed carrier system of the type employing a common transmission line to service a plurality of remote subscriber circuits from a respective plurality of local circuits at a central location, each remote subscriber circuit being paired with a respective local circuit with which it alone communicates, a method comprising the steps of:
- generating at said central location a frequency-stable first carrier signal for each local circuit, the first carrier signal for each local circuit having a different frequency, the frequencies of all of said first carrier signal residing in a first band of frequencies;
- modulating said first carrier signal at each local circuit with externally-derived intelligence signals to derive a single sideband of said first carrier signal, the frequency bandwidth of said intelligence signals being less than the spacing between adjacent first carrier signal frequencies;
- transmitting, from said central location to said remote circuits via said common transmission line, all of said first carrier signals and all of said single sidebands of said first carrier signals;
- at each remote circuit, receiving from said common transmission line the first carrier signal and single sideband thereof for the local circuit with which that remote circuit is paired;
- at each remote circuit, demodulating the received single sideband with the received first carrier signal to recover the externally-derived intelligence signals;
- for all of said remote circuits, generating a translating signal having the same frequency at each remote circuit;
- at each remote circuit, frequency-mixing said translating signal and the received first carrier signal to derive a second carrier signal, the second carrier signals at each remote circuit having different frequencies which reside in a second band of frequencies which does not overlap said first band of frequencies, the frequency difference between the received first carrier signal and the derived second carrier signal being equal to the frequency of said translating signal at all of said remote circuits;
- modulating said second carrier signal at each remote circuit with externally derived further intelligence signals to derive a single sideband of said second carrier signal, the frequency bandwidth of said further intelligence signals being less than the spacing between adjacent second carrier signal frequencies;
- transmitting from each remote circuit to said central location via said common transmission line, said derived single sideband of said second carrier signal;
- at each local circuit, receiving from said common transmission line the single sideband of said second carrier signal transmitted from the remote circuit with which that local circuit is paired;
- providing at each local station a second carrier signal to demodulate the received single sideband;
- and
- at each local circuit, demodulating the received single sideband with the received second carrier signal to recover said further intelligence signal.
A frequency-multiplexed carrier system of the type employing a common transmission line to service a plurality of remote stations from a respective plurality of local stations at a central location, each remote station being paired with a respective local station with which it alone communicates, said system being characterized by:
- generator means for generating at said central location a frequency-stable first carrier signal for each local station, the first carrier signal for each local station having a different frequency, the frequencies of all of said first carrier signals residing in a first band of frequencies;
- modulator means for modulating said first carrier signal at each local station with externally-derived intelligence signals to derive a single sideband of said first carrier signal, the frequency bandwidth of said intelligence signals being less than the spacing between adjacent first carrier signal frequencies;
- transmitter means for transmitting, from said central location to said remote stations via said common transmission line, all of said first carrier signals and all of said single sidebands of said first carrier signals;
- receiver means at each remote station for receiving from said common transmission line the first carrier signal and single sideband thereof for the local station with which that remote station is paired;
- demodulator means at each remote station for demodulating the received single sideband with the received first carrier signal to recover the externally-derived intelligence signals;
- means for providing at all of said remote stations, a common translating signal having the same frequency at each remote station;
- mixer means at each remote station for frequency-mixing said translating signal and the received first carrier signal to derive a second carrier signal, the second carrier signals at each station having different frequencies which reside in a second band of frequencies which does not overlap said first band of frequencies, the frequency difference between the received first carrier signal and the derived second carrier signal being equal to the frequency of said translating signal at all of said remote stations;
- further modulator means for modulating said second carrier signal at each remote station with externally derived further intelligence signals to derive a single sideband of said second carrier signal, the frequency bandwidth of said further intelligence signals being less than the spacing between adjacent second carrier signal frequencies;
- further transmitter means for transmitting, from each remote station to said central location, via said common transmission line, the derived single sideband of said carrier signal;
- further receiver means at each local station for receiving from said common transmission line the single sideband of said second carrier signal transmitted from the remote station with which that local station is paired;
- means for providing at each local station a second carrier signal to demodulate the received single sideband;
- and
- further demodulator means at each local station for demodulating the received single sideband with the second carrier signal to recover said further intelligence signal.
Dependencies are inferred from the claim text.