Tuning indicator system for FM radio receiver

Claim 2

A tuning indicator system for an FM radio receiver, comprising: a first, a second and a third light-emitting means for visual indication of tuning conditions of said receiver; and a tuning indicator circuit operative in association with an output of an FM demodulator included in said receiver for driving said first, second and third light-emitting means, said tuning indicator circuit including circuit means for detecting the level of the dc-voltage component of said demodulator output and circuit means for detecting the level of detuning noise component of said demodulator output, whereby said first light-emitting means becomes energized to emit light by said tuning indicator circuit when said dc-voltage component level is above a predetermined positive reference level, and said second light-emitting means becomes energized to radiate light by said tuning indicator circuit when said dc-voltage component level is below a predetermined negative reference level, and said third light-emitting means becomes energized to emit light by said tuning indicator circuit when said detuning-noise component level is below a predetermined reference level provided that said first and second light-emitting means are de-energized.

Claim 3

A tuning indicator system according to claim 1, in which: said respective light-emitting means comprise light-emitting diodes.

Claim 4

A tuning indicator system according to claim 1, in which: said circuit means for detecting the dc-voltage component level includes a low-pass filter network receiving said demodulator output to produce a dc-voltage signal related to said dc-voltage component of said demodulator output, and includes a first switching means driven by said dc-voltage signal delivered from said low-pass filter network to energize said first light-emitting means when said dc-voltage component level of said demodulator output is above said positive reference level, and further includes a second switching means driven by said dc-voltage signal delivered from said low-pass filter network to energize said second light-emitting means when said dc-voltage component level of said demodulator output is below said negative reference level.

Claim 5

A tuning indicator system according to claim 1, in which: said circuit means for detecting the detuning-noise component level includes: a high-pass filter network receiving said demodulator output to pass said detuning-noise component only; and a smoothed rectifier circuit for rectifying and smoothing said detuning-noise component supplied through said high-pass filter network to produce a dc-voltage signal related with said detuning-noise component, and in which: said third light-emitting means is driven in assoication with said dc-voltage signal produced by said smoothed rectifier circuit.

Claim 6

A tuning indicator system according to claim 1, in which: said tuning indicator circuit includes circuit means for energizing said third light-emitting means in association with said first-mentioned two circuit means.

Claim 7

A tuning indicator system according to claim 5, in which: said circuit means for energizing said third light-emitting means includes a third switching means driven in accordance with the output of said detuning-noise component level detecting circuit means to energize said third light-emitting means, and circuit means associated with said dc-voltage component level detecting circuit means for preventing said third switching means from energizing said third light-emitting means when either one of said first and second light-emitting means is energized.

Claim 8

A tuning indicator system for an FM radio receiver, comprising: a first, a second and a third light-emitting device; a first circuit including a first switching device switched in association with an output of an FM demodulator included in said receiver and connected in series in a current path for energizing said first light-emitting device, and a second switching device switched in association with the demodulator output and connected in series in a current path for energizing said second light-emitting device, said first switching device turning said first light-emitting device on and causing it to emit light when said demodulator output attains a dc-voltage level higher than a predetermined positive reference level, said second switching device turning said second light-emitting device on and causing it to emit light when said demodulator output attains a dc-voltage lower than a predetermined negative reference level; a second circuit including a third switching device switched in association with said demodulator output, said third switching device being turned on when said demodulator output contains detuning-noise component of a level higher than a reference noise level; and a third circuit including a fourth switching device driven in association with said first, second and third switching device and connected to a current path for energizing said third light-emitting device, said fourth switching device being turned on to cause said third light-emitting device to emit light when all of said first, second and third switching devices are turned off.

Claim 9

A tuning indicator system for an FM radio receiver, comprising: a first, a second and a third light-emitting device; a first circuit including a first switching device switched in association with an output of an FM demodulator included in said receiver and connected in series in a current path for energizing said first light-emitting device, and a second switching device switched in association with the demodulator output and connected in series in a current path for energizing said second light-emitting device, said first switching device turning said first light-emitting device on and causing it to emit light when said demodulator output attains a dc-voltage level higher than a predetermined positive reference level, said second switching device turning said second light-emitting device on and causing it to emit light when said demodulator output attains a dc-voltage lower than a predetermined negative reference level; a second circuit including a third switching device switched in association with said demodulator output, said third switching device being turned on when said demodulator output contains detuning-noise component of a level higher than a reference noise level; and a third circuit including a fourth switching device driven in association with said first, second and third switching device and connected to a current path for energizing said third light-emitting device, said fourth switching device being turned on to cause said third light-emitting device to emit light when all of said first, second and third switching devices are turned off.

Claim 10

A tuning indicator system according to claim 7, in which: said first switching device comprises an npn-type transistor having an emitter grounded, a collector connected via said first light-emitting device to a positive voltage supply terminal, and a base supplied with said demodulator output through a low-pass filter network; and said second switching device comprises a pnp-type transistor having an emitter grounded, a collector connected via said second light-emitting device to a negative voltage supply terminal, and a base supplied with said demodulator output through said low-pass filter network.

Claim 11

A tuning indicator system according to claim 8, in which: said fourth switching device comprises an npn-type transistor having a collector connected to said positive voltage supply terminal, an emitter grounded via said third light-emitting device, and a base connected to said third switching device and further connected to the collector of said first switching device via a diode, and in which: said third circuit further includes an npn-type transistor having an emitter connected to said negative voltage supply terminal, a collector connected to said base of said third switching device, and a base coupled to the collector of said second switching device.

Claim 12

A tuning indicator system according to claim 9, in which: said third switching device comprises an npn-type transistor having a base, an emitter grounded, a collector connected to said positive voltage supply terminal via a resistor and to the base of said fourth switching device, and in which: said second circuit further includes a high-pass filter network for passing only the detuning-noise component of said demodulator output, and a smoothed rectifier circuit for rectifying and smoothing said detuning-noise component delivered from said high-pass filter network to thereby produce a dc-voltage related to said detuning-noise component to drive the base of said third switching device.

Claim 13

A tuning indicator system according to claim 8, in which: said fourth switching device comprises an npn-type transistor having a base connected to said third switching device, a collector connected to said positive voltage supply terminal via a resistor, an emitter connected to said negative voltage supply terminal via a resistor, and in which: said third circuit further includes another npn-type transistor having a base grounded, an emitter connected to the emitter of said fourth switching device, and a collector connected to said positive voltage supply terminal via a resistor, said third light-emitting device being connected between the collector of said fourth switching device and the collector of said another transistor.

Claim 14

A tuning indicator system according to claim 11, in which: said third switching device comprises an npn-type transistor having an emitter connected to said negative voltage supply terminal, a collector connected to said positive voltage supply terminal via a resistor, and a base, the base of said fourth switching device being coupled to the collector of said third switching device, and in which: said second circuit further includes: a high-pass filter network for passing only the detuning-noise component of said demodulator output; a smoothed rectifier circuit for rectifying and smoothing the detuning-noise component delivered from said high-pass filter network to thereby produce a dc-voltage related with said detuning-noise component, by which dc-voltage is driven the base of said third switching device; a resistor coupling the collector of said second switching device and the base of said third switching device; and still another pnp-type transistor having a base connected to the collector of said first switching device, an emitter connected to said positive voltage supply terminal, and a collector coupled to the base of said third switching device.

Claim 15

A tuning indicator system according to claim 12, in which: said second circuit further includes a further npn-type transistor forming an emitter-follower circuit through which the detuning-noise component delivered from said high-pass filter network is applied to said smoothed rectifier circuit.