Mitsubishi Denki Kabushiki Kaisha

Kazuo Saito

Yushi Naito

In a public telephone circuit using DCME and DSI, an apparatus with high line efficiency is obtained by demodulating the facsimile signal and transmitting the signal after converting it to a low transmission rate signal. An apparatus of the present invention connected to the exchanger at the trunk side input port comprises bearer interfaces connected to the DCME, FAX modems (3), a multiplexer (4) and a FAX modem discriminator (11). The apparatus demodulates the facsimile signal received from the trunk side input port and transmits the demodulated signal through the transmission line having 64 kbit/s on-demand clear channel under the CCITT recommendation Q. 50.

High efficiency facsimile transmission apparatus

An apparatus for discriminating voice data so as to create statistical data and for discriminating voice/voice band data in digital speech interpolation and digital circuit multiplication equipment. A comparison is made between the dead zone width and the amplitude of the input signal so as to count only how many times the input signal crosses the width of each dead zone as the number of the zero crosses. Then, the sum of the absolute-value voltages of the input signal is determined and the encoding is performed based on the values corresponding to the sum thereof thus determined or the average and dispersion analysis of the values is carried out, thereby effecting the discrimination of the vowel and consonant of the voice, the tone signal and the frequency thereof, and the modulated wave. Further, the number of the crosses of the input signal to the threshold set in the form of plural steps is determined to the input signal transmitted over the telephone line. Then, the encoding is made based on the result of determination of the number of the crosses or the average and dispersion analysis of the values is performed.

Voice/voice band data discrimination apparatus

A speech detector has an intensity detector that indicates whether the intensity of a PCM signal exceeds a first threshold, and a normal-zero-crossing-count detector that indicates whether the zero-crossing count of the PCM signal exceeds a second threshold. The outputs of the intensity detector and normal-zero-crossing-count detector are combined by AND logic to produce the output of the speech detector. The second threshold is set well below the minimum zero-crossing count occurring in normal speech, the function of the normal-zero-crossing-count detector being to disable speech detection during line faults.

Speech detector with improved line-fault immunity

An equalizing circuit comprises a hopping-type amplitude equalizer (70) for changing the characteristics of burst signals inputted sequentially thereto to desired characteristics. The output of the equalizer (70) is distributed by a distributor (23) to a desired number of paths. Each output path of the distributor (23) is provided with a hopping switch (25a, 25b, or 25c), which is operated in synchronism with the amplitude equalizer (70). Consequently, even if the number of signal paths is increased, the number of equalizers required is smaller than the number of signal paths.

Equalizer and equalizing circuit using the same

A variable group delay equalizer comprises a delay portion and an amplitude correcting portion. In the delay portion, a group delay frequency response of an input signal is controlled. In the amplitude correcting portion, an amplitude distortion of the input signal caused in a delay portion can be corrected. A variable group delay equalizer with a wider variable range can be obtained by combining a fixed group delay equalizer.

Equalizer circuit for use in communication unit

An equalizer circuit for use in a communication unit comprises a variable amplitude equalizer (VAE) and a variable group delay equalizer (VDE). The variable amplitude equalizer (VAE) is able to vary only an amplitude frequency response continuously without varying a group delay frequency response, while the variable group delay equalizer (VDE) is able to vary only a group delay frequency response continuously without varying an amplitude frequency response, both being able to adjust the amplitude and group delay frequency responses, respectively, in an independent manner. Preferably, the variable group delay equalizer (VDE) includes an amplitude correcting portion and is structured such that amplitude distortion caused in a delay portion can be corrected by a signal from the amplitude correcting portion.

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Hyogo, Japan

Kazuo Saito