Station disengagement and sensitivity circuit for scan tuned radio receivers

Claim 2

In a radio receiver employing automatic frequency scan circuitry for scanning through a frequency spectrum and stopping its scan in response to and for reception of a received signal of selected signal strength, a circuit comprising: a. means for applying a disabling voltage to a point within said receiver for removing said received signal from said automatic frequency scan circuitry, thereby permitting a scan to commence, b. means for selectively applying an enabling voltage of a first or second level to said point within said receiver during scanning of said frequency spectrum, the first voltage level causing said received signal to be processed through said receiver at a high sensitivity for stopping the scan in response to both weak and strong signals, the second voltage level causing said received signal to be processed through said receiver at a reduced sensitivity for stopping the scan in response to strong signals only, and c. means for restoring said receiver to high sensitivity after stopping of the scan where said second voltage level has been applied to said receiver.

Claim 3

A circuit as in claim 1 which includes a storage device coupled across a tapped impedance, a first switching device for selectively energizing said storage device and a second switching device for coupling said disabling and enabling voltages from said impedance to said receiver.

Claim 4

A circuit as in claim 2 wherein said second switching device couples said disabling and enabling voltages to an amplifier within said receiver for saturating said amplifier in response to said disabling voltage and for controlling the sensitivity of said amplifier in response to said enabling voltage.

Claim 5

In a radio receiver employing automatic frequency scan circuitry for scanning through a frequency spectrum and stopping its scan in response to and for reception of a received signal of selected signal strength, a circuit comprising: a. a storage device, b. a tapped impedance coupled across said storage device, c. a first switching device having first contact means for charging said storage device so as to apply a first voltage characteristic across said impedance, d. said first switching device having second contact means for applying a second voltage characteristic across said impedance and for permitting said device to discharge through said impedance, said storage device being discharged over the duration of a single scan so as to correspondingly reduce the magnitude of the voltage across said impedance, e. a second switching device having first contact means for coupling a terminal on said impedance to a point within said radio receiver for disabling said receiver and permitting a first scan to commence when said first voltage characteristic is applied across said impedance, and for enabling said receiver at a high sensitivity for stopping the first scan in response to both weak and strong signals when said second voltage characteristic is applied across said impedance, f. said second switching device having second contact means coupling a further terminal on said impedance to said point within said radio receiver for disabling said receiver and permitting a second scan to commence when said first voltage characteristic is applied across said impedance and for enabling saiD receiver at a reduced sensitivity for stopping the second scan in response to strong signals only when said second voltage characteristic is applied across said impedance, the high sensitivity of said receiver being restored after the completion of said second scan.

Claim 6

In a radio receiver employing automatic frequency scan circuitry for scanning through a frequency spectrum and stopping its scan in response to and for reception of a received signal of selected signal strength, a circuit comprising: a. a storage device, b. a tapped impedance coupled across said storage device, c. a first switching device having first contact means for charging said storage device so as to apply a first voltage characteristic across said impedance, d. said first switching device having second contact means for applying a second voltage characteristic across said impedance and for permitting said device to discharge through said impedance, said storage device being discharged over the duration of a single scan so as to correspondingly reduce the magnitude of the voltage across said impedance, e. a second switching device having first contact means for coupling a terminal on said impedance to a point within said radio receiver for disabling said receiver and permitting a first scan to commence when said first voltage characteristic is applied across said impedance, and for enabling said receiver at a high sensitivity for stopping the first scan in response to both weak and strong signals when said second voltage characteristic is applied across said impedance, f. said second switching device having second contact means coupling a further terminal on said impedance to said point within said radio receiver for disabling said receiver and permitting a second scan to commence when said first voltage characteristic is applied across said impedance and for enabling saiD receiver at a reduced sensitivity for stopping the second scan in response to strong signals only when said second voltage characteristic is applied across said impedance, the high sensitivity of said receiver being restored after the completion of said second scan.

Claim 7

In a radio receiver employing automatic frequency scan circuitry for scanning through a frequency spectrum and stopping its scan in response to and for reception of a received signal of selected signal strength, a circuit comprising: a. a control capacitor, b. a tapped resistance connected in parallel with said control capacitor between a pair of end terminals, c. a voltage source connected to one of said end terminals, d. a first switching device for selectively connecting said end terminals to a reference voltage point, said capacitor becoming charged by said voltage source when the other of said end terminals is connected to said reference voltage point and being permitted to discharge through said resistance when said one end terminal is connected to said reference voltage point, said capacitor being discharged after the duration of a single scan, e. a second switching device for selectively connecting first and second tap terminals on said tapped resistance to a point within said radio receiver, the selective connection of said first tap terminal applying a disabling voltage within said receiver for permitting a first scan to commence when said other end terminal is connected to said reference voltage point, and applying an enabling voltage that produces a high receiver sensitivity for stopping the first scan in response to both weak and strong signals when said one end terminal is connected to said reference voltage point, the selective connection of said second tap terminal applying a disabling voltage within said receiver for permitting a second scan to commence when said other end terminal is connected to said reference voltage point, and applying an enabling voltage that produces a reduced receiver sensitivity for stopping the second scan in response to strong signals only when said one end terminal is connected to said reference voltage point, high receiver sensitivity being restored after the completion of said second scan.

Claim 8

In a radio receiver employing automatic frequency scan circuitry for scanning through a frequency spectrum and stopping its scan in response to and for reception of a received signal of selected signal strength, a circuit comprising: a. a control capacitor, b. a tapped resistance connected in parallel with said control capacitor between a pair of end terminals, c. a voltage source connected to one of said end terminals, d. a first switching device for selectively connecting said end terminals to a reference voltage point, said capacitor becoming charged by said voltage source when the other of said end terminals is connected to said reference voltage point and being permitted to discharge through said resistance when said one end terminal is connected to said reference voltage point, said capacitor being discharged after the duration of a single scan, e. a second switching device for selectively connecting first and second tap terminals on said tapped resistance to a point within said radio receiver, the selective connection of said first tap terminal applying a disabling voltage within said receiver for permitting a first scan to commence when said other end terminal is connected to said reference voltage point, and applying an enabling voltage that produces a high receiver sensitivity for stopping the first scan in response to both weak and strong signals when said one end terminal is connected to said reference voltage point, the selective connection of said second tap terminal applying a disabling voltage within said receiver for permitting a second scan to commence when said other end terminal is connected to said reference voltage point, and applying an enabling voltage that produces a reduced receiver sensitivity for stopping the second scan in response to strong signals only when said one end terminal is connected to said reference voltage point, high receiver sensitivity being restored after the completion of said second scan.

Claim 9

A circuit as in claim 5 wherein said second switching device couples said disabling and enabling voltages to an amplifier within said receiver for saturating said amplifier in response to said disabling voltage and for controlling the sensitivity of said amplifier in response to said enabling voltage.

Claim 10

A circuit as in claim 6 wherein said first tap terminal is joined to said one end terminal and said second terminal tap is at an intermediate point on said resistance between said pair of end terminals.

Claim 11

A circuit as in claim 7 wherein said voltage source is of positive potential and said reference voltage point is at ground.