Abstract: The invention is to provide a more economical and practical multi-channel inverter with reference particularly to a modulation process of the time width, wherein a DC output is fed to each of a multiplicity of output channel circuits through time division to a multi-channeling, each of the time widths is modulated pertinently according to each output, thereby obtaining DC and AC multi-channel outputs independently of each other between said channels.

Abstract: Disclosed is a disc or tape signal reproducing apparatus having a first speed control loop in which the duration of a specific pulse in the PCM signal recorded on the disc or tape is detected and the current sync signal interval is anticipated from the duration of the pulse so that the motor speed is pulled into the operation range of the sync signal detector, and a second speed control loop which controls the motor speed basing on the sync signal reproduced by the sync signal detector. The motor speed is controlled by the first speed control loop until the sync signal detector detects the sync signal, thereafter the motor speed is controlled by the second speed control loop basing on the reproduced sync signal.

Abstract: A drive circuit for an electroluminescent (EL) element whose brightness can be changed by changing a voltage or the frequency of the voltage applied to the EL element and can be kept constant by keeping the current flowing through the EL element constant is disclosed. The drive circuit is provided with a drive power source whose output voltage or output voltage frequency is variable by a control signal. The output of the drive power source is supplied to the EL element. The current flowing through the EL element is detected by a current detecting element and a signal related to the detected current is applied as the control signal to the drive power source to subject the EL element to a constant-current drive.

Abstract: A digital audio disc (DAD) reproducing apparatus comprises pulse width detection and pulse width-to-voltage conversion means for detecting a signal having a predetermined pulse width such as a maximum or minimum pulse width of code modulated digital data signals reproduced by a pickup and converting the detected signal to a voltage proportional to the pulse width, and pulse width error detection means for detecting an error between the converted voltage and a reference voltage corresponding to a reference pulse width. Since the pulse width of the digital data signal changes with a clock rate, the error from the reference voltage represents an error in the clock rate.

Abstract: An improved antenna tuning circuit for a long and a medium wave AM radio receiver is disclosed. The antenna tuning circuit of the present invention comprises a tuning coil wound around a ferrite core, a variable capacitor connected in parallel with the tuning coil, and a field effect transistor. One end of the tuning coil is connected to the gate electrode directly or through an impedance means, while the other end of the tuning coil is grounded. The output signal of the antenna tuning circuit is taken out from a selected one of the source or drain electrode of the field effect transistor, whereby the signal to noise ratio may be remarkably improved.

Abstract: In a dynamic drive circuit for light-emitting diodes, at least one of the rise and fall times of the current flowing through the light-emitting diode is elongated to reduce the higher harmonic components contained in the current.

Abstract: A variable impedance circuit comprises an amplifier with a high input impedance and a high output impedance whose gain is variable in response to a control voltage, an emitter-follower transistor, and an impedance element adapted to feedback an output signal to an input terminal of the amplifier. The input terminal of the amplifier and the input terminal of the emitter-follower transistor are connected in common. The emitter-follower transistor has its output terminal connected in series with the output terminal of the amplifier through a load resistor. An impedance of the amplifier as viewed from its input terminal is multiplied by Miller effect and varied in value by the control signal to a great extent.