Hitachi, Ltd.

Kosaku Aida

Tetsuya Nakagawa

Yasuaki Takahara

Nobuya Kasai

Mark Walton

Eiji Kubo

A semiconductor device comprises a DSP (Digital Signal Processor), a CPU for controlling the DSP and an interface circuit. The interface circuit comprises an input circuit, a gain-adjusting circuit and an output circuit. The input circuit inputs a digital signal and supplies the signal to the DSP synchronously with a first clock signal. The gain-adjusting circuit is capable of adjusting the gain of the digital signal supplied to the input circuit. The output circuit adds a digital signal received from the DSP to the digital signal with the gain thereof adjusted and outputs a signal obtained as a result of the addition synchronously with the first clock signal. A signal path extended from the input circuit through the gain-adjusting circuit to the output circuit forms hardware. A digital signal to be transmitted propagates through the hardware to be subjected to the so-called side-tone processing. As a result, it is possible to provide a semiconductor device capable of generating a side tone without increasing the magnitude of a load borne by a CPU and without requiring an external circuit component.

Semiconductor device

A cordless telephone apparatus has a base station connected to a public telephone network and assigned with a specific identification code and one or more personal stations linked to the base station through the medium of radio frequencies. The base station has one or more additional functions in addition to the speech function. The personal station can perform radio communications with the base station within a range in which radio waves from the base station is receivable and can perform radio communications with a cell station connected to a public telephone network outside the radio wave receivable range. The personal station has a remote-control instruction unit for instructing operation of the additional function of the base station. The personal station has a communication station decision unit for deciding which one of the base station and cell station can radio-communicate with the personal station, a storage unit for storing a specific identification code of the base station and a control code corresponding to the additional function, a DTMF signal generation unit for converting the given control code into a DTMF signal in accordance with a predetermined conversion rule, and a controller.

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Adachi, Japan

Kosaku Aida