An input signal is applied to a first limiting amplifier circuit, and an output of the first limiting amplifier circuit is applied to a second limiting amplifier circuit. An output of the second limiting amplifier circuit is applied to a third limiting amplifier circuit. The output signal of the first limiting amplifier circuit is applied to a first detector circuit, the output signal of the second limiting amplifier circuit is applied to a second detector circuit, and the output signal of the third limiting amplifier circuit is applied to a third detector circuit. Bias means for stipulating the bias states of the first, second and third detector circuits are coupled to the third detector circuit. An output signal of the third detector circuit is applied to the second detector circuit as a bias signal, and an output signal of the second detector circuit is applied to the first detector circuit as a bias signal. An output signal of the first detector circuit exhibits a level corresponding to the sum among the output signals of the first, second and third limiting amplifier circuits.

Signal strength detecting circuit

A signal processing circuit for an FM signal receiver suitable for constructing in an integrated circuit is disclosed. The signal processing circuit comprises a differential amplifier circuit receiving first and second demodulated signals of the frequency modulated signal and providing first and second output signals. A current switching circuit has a first input point for receiving the second output signal of the amplifier and a second input point for receiving the output of a constant current source. The current switching circuit switches current paths from the first and second input points to first and second output points in response switching control inputs. A first current mirror has an input point coupled to the second output point of the current switching circuit and an output point coupled to the first output signal of the amplifier circuit. A second current mirror has an input point coupled to the first output point of the current switching circuit, a first output point coupled to the output point of the first current mirror and a second output point coupled to an output terminal. A null-centered indicator is connected between a reference voltage terminal and the junction of the output point of the first current mirror and the first output point of the second current mirror. A potential difference detector can be inserted between the reference voltage terminal and the null-centered indicator.

Signal processing circuit for an FM signal receiver

A display device includes a single meter which can be selectively employed as a signal meter indicating a strength level of a received radio wave and an output level meter indicating an output level of an amplifier. The display device is so designed that the meter is automatically caused to operate as the signal meter when a person touches the tuning knob of a tuner section, otherwise the meter operates as the output level meter. A switch may be provided to restrict the meter function to that of the signal meter regardless of a person's touching of the tuning knob.

Display device in electrical equipment

The radio receiver has an antenna and an arrangement for monitoring the electromagnetic and/or electrostatic field produced by a radio transmitter in the region of the receiver. The monitoring arrangement determines a control parameter for the electromagnetic and/or electrostatic field.The radio receiver itself transmits and/or displays a signal or information when the control parameter deviates from a stored control parameter. The information or signal can be transmitted by the receiver in acoustic, visual electromagnetic or other form.

Radio receiver monitoring system

A receiver has a first input circuit and a first amplifier connected to a first rectifier circuit and has a second input circuit and a second amplifier connected to a second rectifier circuit. The first and second rectifier circuits produce first and second direct current signals, and the first and second rectifier circuits are connected to a meter drive circuit which produces a direct current signal in response to the first or second direct current signal so that the direct current signal from the meter drive circuit actuates a meter to indicate the input level of either the first input circuit or second input circuit.

Mitsuo Ohsawa

Papers

Input level display circuit for receivers

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