Squench circuit with time delay variable in accordance with strength of received signal

Claim 2

A squelch control circuit operated in response to a detected noise voltage including iN combination: filter means having a particular time constant and adapted to receive the detected noise voltage and being responsive thereto to develop a filtered noise voltage; switch means responsive to an input voltage greater than a first predetermined threshold to be actuated thereby; means coupling said filter means with the input of said switch means to apply said filtered noise voltage thereto; charge storage means having a time constant greater than said particular time constant coupled with the output of said switch means for storing a predetermined charge in response to actuation of said switch means to produce a first voltage; comparator means having first and second inputs and responsive to a voltage at said first input greater than the voltage at said second input to produce a control voltage; circuit means coupling said charge storage means with said first input of said comparator means for applying said first voltage thereto; reference voltage means coupled with said second input of said comparator means for applying a reference voltage thereto; and control means coupled to said filter means and providing a control action varying with said filtered noise voltage, said control means being further coupled to one of said charge storage means and said reference voltage means, for changing one of said first voltage and said reference voltage, respectively, in accordance with the level of said filtered noise voltage, to thereby control the development of said control voltage by said comparator means.

Claim 3

A squelch control circuit in accordance with claim 1 wherein said control means includes capacitor means, means for charging said capacitor means to a value related to the value of said filtered noise voltage, and means coupled to said capacitor means having a current path controlled by the voltage across said capacitor means.

Claim 4

A squelch control circuit in accordance with claim 1 wherein said control means is coupled to said reference voltage means and acts to increase said reference voltage in response to an increase in said filtered noise voltage.

Claim 5

A squelch control circuit in accordance with claim 1 wherein said charge storage means includes capacitor means for providing a first voltage of a fixed value, and wherein said reference voltage means includes voltage divider means which provides a reference voltage less than said fixed value, said control means being coupled to said voltage divider means and causing said reference voltage to vary with said filtered noise voltage.

Claim 6

A squelch control circuit in accordance with claim 4 wherein said control means includes delay means for delaying the action of said control means on said reference voltage means when the filtered noise voltage drops.

Claim 7

A squelch control circuit in accordance with claim 4 wherein said control means includes further capacitor means, means for charging said further capacitor means to a voltage related to said filtered noise voltage, and impedance means controlled by the voltage across said further capacitor means and connected to said voltage divider for changing the reference voltage provided thereby.

Claim 8

A squelch control circuit in accordance with claim 1 wherein said control means is coupled to said charge storage means and acts to reduce the charge stored thereby in response to actuation of said switch means so that said first voltage varies inversely with the level of said filtered noise voltage.

Claim 9

A squelch control circuit in accordance with claim 7 wherein said charge storage means includes capacitor means across which a voltage is developed, and wherein said reference voltage means provides a fixed reference voltage, with the voltage developed across said capacitor means in response to actuation of said switch means being greater than said fixed reference voltage and varying inversely with the value of said filtered noise voltage.

Claim 10

A squelch control circuit in accordance with claim 8 wherein said control means incLudes delay means for delaying the action thereof to increase the voltage across said capacitor means as the value of the filtered noise voltage decreases.

Claim 11

A squelch control circuit in accordance with claim 8 wherein said control means includes a further capacitor and means operating to charge said further capacitor to a voltage related to said filtered noise voltage, and wherein said charge storage means includes means for charging said capacitor means which is coupled to said further capacitor and which provides a charging voltage for said capacitor means which varies inversely with the voltage across said further capacitor.

Claim 12

A squelch control circuit in accordance with claim 7 wherein said comparator means has a third input effectively in parallel with said first input, and said comparator means responds to a voltage at one of said first and third inputs which is greater than the voltage at said second input to produce the control voltage, said reference voltage means provides a fixed reference voltage which is greater than said first voltage produced by said charge storage means in response to said filtered noise voltage rising above a particular value, and means coupling said filter means to said third input of said comparator means to apply a voltage thereto to control said comparator means upon the voltage at said first input thereof falling below said reference voltage at said second input.

Claim 13

A squelch control circuit in accordance with claim 11 wherein said means coupling said filter means to said third input of said comparator includes level shift means for applying a third voltage to said third input of said comparator means so that said comparator means continues to produce said control voltage, said level shift means causing said third voltage to drop in response to a drop in said filtered noise voltage to rapidly terminate said control voltage.

Claim 14

A squelch control circuit operated in response to a detected noise voltage provided at a first terminal for providing a control voltage at a second terminal, and including in combination: charge storage means for storing a predetermined charge to produce a first voltage; threshold means coupling said charge storage means to the first terminal and causing said charge storage means to produce said first voltage in response to a detected noise voltage which exceeds a predetermined value; comparator means having first and second inputs and an output connected to the second terminal, said comparator means being responsive to a voltage at said first input greater than the voltage at said second input to develop a control voltage at said output; circuit means coupling said charge storage means to said first input of said comparator means for applying said first voltage thereto; reference voltage means coupled to said second input of said comparator means for applying a reference voltage thereto which has a value less than said first voltage, so that said comparator means produces the control voltage in response to a detected noise voltage which exceeds said predetermined value; and control means coupled to said first terminal and providing a control action varying with said detected noise voltage, said control means being further coupled to one of said charge storage means and said reference voltage means, for changing one of said first voltage and said reference voltage, respectively, in accordance with the level of said detected noise voltage, to thereby control the action of said comparator means to terminate the control voltage when the detected noise voltage drops below said predetermined value.

Claim 15

A squelch control circuit operated in response to a detected noise voltage provided at a first terminal for providing a control voltage at a second terminal, and including in combination: charge storage means for storing a predetermined charge to produce a first voltage; threshold means coupling said charge storage means to the first terminal and causing said charge storage means to produce said first voltage in response to a detected noise voltage which exceeds a predetermined value; comparator means having first and second inputs and an output connected to the second terminal, said comparator means being responsive to a voltage at said first input greater than the voltage at said second input to develop a control voltage at said output; circuit means coupling said charge storage means to said first input of said comparator means for applying said first voltage thereto; reference voltage means coupled to said second input of said comparator means for applying a reference voltage thereto which has a value less than said first voltage, so that said comparator means produces the control voltage in response to a detected noise voltage which exceeds said predetermined value; and control means coupled to said first terminal and providing a control action varying with said detected noise voltage, said control means being further coupled to one of said charge storage means and said reference voltage means, for changing one of said first voltage and said reference voltage, respectively, in accordance with the level of said detected noise voltage, to thereby control the action of said comparator means to terminate the control voltage when the detected noise voltage drops below said predetermined value.

Claim 16

A squelch control circuit in accordance with claim 13 wherein said control means is coupled to said reference voltage means and acts to increase said reference voltage in response to an increase in the detected noise voltage at the first terminal.

Claim 17

A squelch control circuit in accordance with claim 13 wherein said control means is coupled to said charge storage means and Acts to reduce said first voltage in response to an increase in the detected noise voltage at the first terminal.