Abstract: An apparatus for testing semiconductor IC chips including a first tester, a second tester, a test program control section, and a distribution control section. The test program control section supplies data representing a plurality of test items, to the first tester. The first tester determines the characteristics of the semiconductor IC chips of each lot, for each test item. The data representing the characteristics of the IC chips, thus determined for each test item, is supplied to the distribution control section. The distribution control section finds the distribution of the characteristics of the IC chips, and determines whether the distribution is within a predetermined range. If the characteristic distribution is within the range, the distribution control section supplies data representative of the number assigned to the test item to the test program control section, and the test program control section, then deletes the test item corresponding from data supplied to the second tester.

Abstract: A sampled data generation circuit includes a voltage controlled oscillator for producing an output signal with a frequency variable according to a control voltage, a sample and hold circuit for sampling and holding an analog input signal in response to the output signal from the voltage controlled oscillator, and a control circuit for detecting the difference between two successive sampled data generated from the sample and hold circuit and supplying the voltage controlled oscillator with an output signal corresponding to the difference as the control voltage, thereby controlling the voltage controlled oscillator so that the greater the difference, the higher the frequency of the output signal from the voltage controlled oscillator is.

Abstract: A noise reduction system having an encoder which compresses the dynamic range of an analog audio signal, a transmission medium coupled to the encoder, and a decoder coupled to the transmission medium for expanding and thereby restoring the dynamic range of the compressed analog audio signal. The encoder includes a voltage controlled amplifier (VCA) receiving the audio signal, a high-pass filter also coupled to the analog audio signal, a circuit for obtaining a difference between the outputs of the VCA and the high-pass filter, weighting and level sensing circuits coupled to the encoder output for sensing the level of the compressed analog audio signal, and a limiter circuit coupled to the output of the weighting and level sensing circuits and producing a control voltage applied to the VCA control input in such a manner that the ratio of the gain of the VCA and the gain of the high-pass filter at the pass band thereof does not become less than one.

Abstract: A noise reduction system is provided with an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude of the input signal and recording the compressed one into a tape-recorder, and a decoder for expanding the dynamic range of a reproduced audio signal from the tape-recorder to the original one in accordance with the amplitude of the reproduced audio signal. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is low- and middle-levels, sufficient emphasis is made to the signal at high-frequencies, and when it is in high-level, the emphasis quantity at high-frequencies is restrictive. The decoder includes a second controlled amplifier circuit having a transfer function related to the character of the first controlled amplifier circuit substantially in inverse-function manner.

Abstract: A noise reduction system including an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude thereof, a transmission medium coupled to the encoder, and a decoder having a transfer function inverse to that of the decoder. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is in low- and middle- levels, sufficient emphasis is made to the signal at high frequencies, and when it is in high-level, the emphasis quantity at high frequencies is restrictive. The decoder includes a voltage-current converting circuit for converting voltage of the reproduced audio signal into current and a second controlled amplifier circuit amplifying the converted current and having a transfer function inverse to that of the first controlled amplifier circuit.

Abstract: A noise reduction system is provided with an encoder for compressing the dynamic range of an audio input signal in accordance with the amplitude of the input signal and recording the compressed one into a tape recorder, and a decoder for expanding the dynamic range of a reproduced audio signal from the tape recorder to the original one in accordance with the amplitude of the reproduced audio signal. The encoder includes a first controlled amplifier circuit in which, when the input audio signal is in low- and middle-levels, sufficient emphasis is made to the signal at high frequencies, and when it is in high-level, the emphasis quantity at high frequencies is restrictive. The decoder includes a second controlled amplifier circuit having a transfer function related to the character of the first controlled amplifier circuit substantially in inverse-function manner.