Monitoring circuit and system for detecting signals in a signal transmission system

Claim 2

A monitoring circuit for use in a signal transmission system for transmitting signals via a signal transmission medium comprising: detecting means adapted to be coupled to said signal transmission medium for detecting the presence and absence of signals transmitted via said signal transmission medium, said detecting means including a rectifying means for rectifying the transmitted signals and a comparing means for comparing the output voltage of said rectifying means with a reference voltage; a gated oscillator connected to said detecting means for providing an output signal at a carrier frequency when said detecting means detects the absence of the transmitted signals; modulating means connected to said gated oscillator for modulating said output signal with a sinusoidal code signal of a particular frequency to provide a coded signal representative of the monitoring circuit; and means adapted to couple said modulating means to said signal transmission medium for transmitting said coded signal, said coded signal being capable of causing subsequent monitoring circuits to detect the presence of transmitted signals.

Claim 3

A monitoring circuit for use in a signal transmission system as defined in claim 1 wherein said signal transmission medium includes at least two cable segments coupled by an amplifier and the signals transmitted include television signals, said monitoring circuit adapted to be coupled between the two cable segments.

Claim 4

A monitoring circuit as defined in claim 1 wherein the transmitted signals include a pilot signal of a particular frequency, said detecting means includes discriminating means for separating said pilot signal from the remaining transmitted signals, said detecting means detects the presence and absence of said pilot signal, and said output signal of said gated oscillator has a frequency of said pArticular frequency of said pilot signal.

Claim 5

A monitoring circuit as defined in claim 3 wherein said discriminating means includes a tuned amplifier with a passband tuned about the frequency of said pilot signal.

Claim 6

A monitoring circuit as defined in claim 3 wherein said rectifying means rectifies said pilot signal from said discriminating means.

Claim 7

A monitoring circuit as defined in claim 5 wherein said pilot signal is of a frequency within the frequencies of the transmitted signals and said discriminating means include a tuned amplifier with a passband tuned about the frequency of said pilot signal.

Claim 8

A signal transmission system for transmitting television signals via a cable including cable segments coupled by amplifiers for maintaining the signal strength of the television signals and a plurality of monitoring circuits spaced along said cable and coupled between segments thereof, each of said monitoring circuits comprising: input means coupled to a first cable segment; detecting means connected to said input means for detecting the presence and absence of signals on said first cable segment, said detecting means including a rectifying means for rectifying the signals coupled from said first cable segment and a comparing means for comparing the output voltage of said rectifying means with a reference voltage; a gated oscillator connected to said detecting means for providing an output signal of a carrier frequency when said detecting means detects the absence of signals on said first cable segment; modulating means connected to said gated oscillator for modulating said output signal with a code comprising a sinusoidal signal of a particular frequency to provide a coded signal representative of the particular monitoring circuit; and means coupling said modulating means to a second cable segment, said coded signal being capable of causing the detecting means of subsequent monitoring circuits to detect the presence of signals.

Claim 9

A signal transmission system for transmitting television signals via a cable including cable segments coupled by amplifiers for maintaining the signal strength of the television signals and a plurality of monitoring circuits spaced along said cable and coupled between segments thereof, each of said monitoring circuits comprising: input means coupled to a first cable segment; detecting means connected to said input means for detecting the presence and absence of signals on said first cable segment, said detecting means including a rectifying means for rectifying the signals coupled from said first cable segment and a comparing means for comparing the output voltage of said rectifying means with a reference voltage; a gated oscillator connected to said detecting means for providing an output signal of a carrier frequency when said detecting means detects the absence of signals on said first cable segment; modulating means connected to said gated oscillator for modulating said output signal with a code comprising a sinusoidal signal of a particular frequency to provide a coded signal representative of the particular monitoring circuit; and means coupling said modulating means to a second cable segment, said coded signal being capable of causing the detecting means of subsequent monitoring circuits to detect the presence of signals.

Claim 10

A signal transmission system as defined in claim 7 wherein the television signals include a pilot signal of a particular frequency, and said detecting means of each monitoring circuit includes discriminating means for separating said pilot signal from the remaining transmitted signals, said detecting means of each monitoring circuit detects the presence and absence of said pilot signal, and said coded signal has a carrier frequency of said particular frequency of said pilot signal.

Claim 11

A signal transmission system as defined in claim 8 wherein said discriminating means of each monitoring circuit includes a tuned amplifier with a passband tuned about said particular frequency of said pilot signal.

Claim 12

A signal transmission system as defined in claim 8 in combination with a receiver station coupled to one of said cable segments for detecting the code and for providing an output indication of the particular one of the monitoring circuits that generated the code.

Claim 13

A signal transmission system as defined in claim 7 in combination with a receiver station connected to one of said cable segments for detecting the code and for providing an output indication of the particular one of the monitoring circuits that generated the code.