Priority channel scanning system with dual response time control

Claim 2

A channel scanning and priority channel monitoring system for use with a radio receiver of the superheterodyne type for receiving signals on a predetermined number of channels, with one channel being designated a priority channel, which receiver has mixing means operative to provide reception on different channels, and oscillator means connected to the mixing means for providing signals to the mixing means at different frequencies corresponding to the different channels, said channel scanning and priority system including in combination: pulse responsive switching means having at least first and second conditions of operation; means for coupling said switching means to said oscillator means for controlling the output frequency of said oscillator means in accordance with the condition of operation of said switching means; clock means coupled to said switching means for providing clock pulses thereto at first and second predetermined frequencies, said clock pulses causing said switching means to change condition of operation; detector means for detecting the presence of a received signal on the channel associated with the output frequency of the oscillator; means coupling said detector means to said clock means for causing said clock means to provide pulses at said first frequency in the absence of a received signal and at said second frequency upon receipt of a signal; delay means coupled to said clock means for delaying the application to said switching means of said pulses of said first frequency for a predetermined time duration following termination of a received signal; and means coupled to said switching means and responsive to a predetermined condition of operation of said switching means for maintaining said switching means in said predetermined condition of operation upon receipt of a signal on a channel associated with said predetermined condition of operation.

Claim 3

A system as recited in claim 1 wherein said detector means includes control means for varying the response time thereof.

Claim 4

A system as recited in claim 2 further including means responsive to the strength of the received signal so that said response time is longer for weak signals than for strong signals.

Claim 5

A system as recited in claim 2 further including means coupled to said switching means and responsive to said predetermined condition of operation thereof for decreasing the response time of said detector means.

Claim 6

A system as recited in claim 4 wherein said means for coupling said switching means to said oscillator means includes selector means for controlling said oscillator means to provide an output signal of the frequency to operate said mixing means and provide reception by said radio receiver of signals on a priority channel upon operation of said switching means to said predetermined condition.

Claim 7

A system as recited in claim 1 wherein said clock means includes a first clock for providing pulses at said first predetermined frequency, and a second clock for providing pulses at said second predetermined frequency.

Claim 8

A system as recited in claim 1 wherein said means for maintaining said switching means in said predetermined condition of operation includes gate means coupled to said switching means for making said switching means non-responsive to pulses from clock means.

Claim 9

A system as recited in claim 1 wherein said sWitching means includes a counting circuit having a plurality of stages in excess of two.

Claim 10

A system as recited in claim 1 wherein said radio receiver includes an audio amplifier and audio reproducing means and further includes means for attenuating the signals applied to the audio amplifier, said attenuating means being operated in response to output pulses from said clock means.

Claim 11

A system as recited in claim 9 wherein said receiver includes alternating current signal responsive squelch means coupled to said audio amplifier for interrupting the signals applied to said audio amplifier in response to said alternating current signals.

Claim 12

A system as recited in claim 10 further including squelch control oscillator means coupled to said detector means and responsive thereto for generating alternating current signals in response to control signals from said detector means, said squelch control oscillator means being further coupled to said squelch means for control thereof in response to said detector means.

Claim 13

A system as recited in claim 11 wherein said receiver further includes modulation detection means and second switch means for selectively coupling said modulation detection means to one of said squelch means and said detector means.

Claim 14

A channel scanning system for use with a radio receiver for receiving signals on a predetermined number of channels, including in combination, pulse reponsive switching means for selecting one of said predetermined channels, means for coupling said switching means to said receiver, pulse producing means having first and second conditions of operation connected to said switching means for causing said switching means to change channels in response to said pulses, detector means for connection to said receiver for detecting the presence of a signal on a channel and for altering the condition of operation of said pulse producing means upon receipt of a signal by said receiver, said detector means including means for varying the response time of said detector means in response to the strength of the signal being received by said receiver, and delay means coupled to said pulse producing means for maintaining the altered condition of operation of said pulse producing means for a predetermined time duration following the termination of said signal.

Claim 15

A channel scanning system for use with a radio receiver for receiving signals on a predetermined number of channels, including in combination, pulse reponsive switching means for selecting one of said predetermined channels, means for coupling said switching means to said receiver, pulse producing means having first and second conditions of operation connected to said switching means for causing said switching means to change channels in response to said pulses, detector means for connection to said receiver for detecting the presence of a signal on a channel and for altering the condition of operation of said pulse producing means upon receipt of a signal by said receiver, said detector means including means for varying the response time of said detector means in response to the strength of the signal being received by said receiver, and delay means coupled to said pulse producing means for maintaining the altered condition of operation of said pulse producing means for a predetermined time duration following the termination of said signal.

Claim 16

A system as recited in claim 13 wherein said detector means includes means for reducing the response time of said detector means in response to pulses from said pulse producing means.

Claim 17

A radio receiver of the superheterodyne type for receiving signals on a predetermined number of channels including in combination: mixing means operative to provide reception by said radio receiver on said predetermined channels; oscillator means connected to said mixing means for providing output signals to said mixing means at different frequencies corresponding to said predetermined channels; pulse responsive switching means, having at least first and second conditions of operation, coupled to said oscillator means for controlling the output frequency of said oscillator means in accordance with the condition of operation of said switching means; first clock pulse producing means coupled to said switching means for providing clock pulses thereto at a first predetermined frequency, said clock pulses causing said switching means to change condition of operation; second clock pulse producing means coupled to said switching means for providing clock pulses thereto at a second predetermined frequency for causing said switching means to change condition of operation; detector means coupled to said receiver for detecting a received signal, said detector means being coupled to said first and second clock means for causing said first clock means to operate said switching means in the absence of a received signal, and for causing said second clock means to operate said switching means in the presence of a received signal; delay means coupled to said first clock pulse pRoducing means for delaying the application of said first frequency pulses to said switching means for a predetermined time duration following termination of a received signal; and means coupled to said detector means for varying the responsse time thereof in accordance with the strength of the signal being received by said receiver, and for reducing the response time of said switching means for a predetermined time duration following a predetermined change in the condition of operation of said switching means.

Claim 18

A radio receiver of the superheterodyne type for receiving signals on a predetermined number of channels including in combination: mixing means operative to provide reception by said radio receiver on said predetermined channels; oscillator means connected to said mixing means for providing output signals to said mixing means at different frequencies corresponding to said predetermined channels; pulse responsive switching means, having at least first and second conditions of operation, coupled to said oscillator means for controlling the output frequency of said oscillator means in accordance with the condition of operation of said switching means; first clock pulse producing means coupled to said switching means for providing clock pulses thereto at a first predetermined frequency, said clock pulses causing said switching means to change condition of operation; second clock pulse producing means coupled to said switching means for providing clock pulses thereto at a second predetermined frequency for causing said switching means to change condition of operation; detector means coupled to said receiver for detecting a received signal, said detector means being coupled to said first and second clock means for causing said first clock means to operate said switching means in the absence of a received signal, and for causing said second clock means to operate said switching means in the presence of a received signal; delay means coupled to said first clock pulse pRoducing means for delaying the application of said first frequency pulses to said switching means for a predetermined time duration following termination of a received signal; and means coupled to said detector means for varying the responsse time thereof in accordance with the strength of the signal being received by said receiver, and for reducing the response time of said switching means for a predetermined time duration following a predetermined change in the condition of operation of said switching means.

Claim 19

A system as recited in claim 15 wherein said first clock pulse producing means includes a first astable multivibrator coupled to said detector means responsive thereto for providing said first frequency pulses in the absence of a received signal by said receiver.

Claim 20

A system as recited in claim 16 further including a monostable multivibrator coupled to said first astable multivibrator and responsive thereto for providing pulses having a time duration substantially equal to one-half of the time interval between pulses of said first clock for changing the condition of operation of said switching means.

Claim 21

A system as recited in claim 17 wherein said second clock pulse producing means includes a second astable multivibrator coupled to said detector means and responsive thereto for providing said second frequency pulses in the presence of a received signal.

Claim 22

A system as recited in claim 18 wherein said monostable multivibrator is further coupled to said second astable multivibrator responsive thereto for changing the condition of operation of said switching means.

Claim 23

A system as recited in claim 15 wherein said delay means is interposed between said detector means and said first clock pulse producing means, and includes a capacitor for delaying the operation of said first clock for a predetermined time duration following the termination of a received signal.

Claim 24

A system as recited in claim 15 further including indicator means coupled to said switching means and responsive thereto for visually indicating the channel being monitored.

Claim 25

A radio receiver of the superheterodyne type for receiving signals on a predetermined number of channels including in combination: mixing means operative to provide reception by said radio receiver on said predetermined channels; oscillator means connected to said mixing means for providing output signals to said mixing means at different frequencies corresponding to said predetermined channels, said mixing means providing intermediate frequency signals in response to said output signals; intermediate frequency amplifier means coupled to said mixing means for receiving and amplifying said intermediate frequency signals from said mixing means; modulation detection means coupled to said intermediate frequency means for receiving said amplified intermediate frequency signals and detecting the modulation thereon, said modulation detection means providing signals in response to said modulation; amplifier means coupled to said detection means for receiving and amplifying said signals therefrom; signal detector means coupled to one of said modulation detection and intermediate frequency amplifier means for detecting the strength of any signal received by said receiver and for providing a control signal in response thereto; alternating current signal responsive muting means coupled to said audio amplifier means for rendering said amplifier means substantially non-responsive to said signals received from said modulation detection means; and alternating current signal generating means coupled to said signal detector means and to said muting means, said alternating current signal generating means being responsive to said control signals for providing alternating current signals to operate said muting means in response to said control signals from said detection means.

Claim 26

A radio receiver of the superheterodyne type for receiving signals on a predetermined number of channels including in combination: mixing means operative to provide reception by said radio receiver on said predetermined channels; oscillator means connected to said mixing means for providing output signals to said mixing means at different frequencies corresponding to said predetermined channels, said mixing means providing intermediate frequency signals in response to said output signals; intermediate frequency amplifier means coupled to said mixing means for receiving and amplifying said intermediate frequency signals from said mixing means; modulation detection means coupled to said intermediate frequency means for receiving said amplified intermediate frequency signals and detecting the modulation thereon, said modulation detection means providing signals in response to said modulation; amplifier means coupled to said detection means for receiving and amplifying said signals therefrom; signal detector means coupled to one of said modulation detection and intermediate frequency amplifier means for detecting the strength of any signal received by said receiver and for providing a control signal in response thereto; alternating current signal responsive muting means coupled to said audio amplifier means for rendering said amplifier means substantially non-responsive to said signals received from said modulation detection means; and alternating current signal generating means coupled to said signal detector means and to said muting means, said alternating current signal generating means being responsive to said control signals for providing alternating current signals to operate said muting means in response to said control signals from said detection means.

Claim 27

A radio receiver as recited in claim 22 wherein said modulation detection means includes a discriminator providing modulation and noise signals, and said signal detector means includes a first squelch circuit connected to said discriminator and responsive to the noise signals provided by said discriminator, said alternating current signal responsive muting means including a second noise responsive squelch circuit connected to said alternating current signal generating means, and wherein said alternating current signal generating means includes means responsive to said first squelch circuit for providing signals for actuating said second squelch circuit, said last mention signals being generated in response to the noise signals received by said first squelch for causing said second squelch circuit to mute said receiver in response to noise signals received by said first squelch circuit.

Claim 28

A radio receiver as recited in claim 23 further including switch means connected to said discriminator and said first and second squelch circuits for selectively coupling one of said first and second squelch circuits to said discriminator.