Fujitsu Corporation

Hideki Shutou

Koji Ikeda

Osamu Kobayashi

Minoru Takeno

Fumihiro Suenaga

A constant voltage drive type driver circuit includes a pulse transformer for outputting output pulses having a predetermined peak value and having primary and primary windings. The secondary winding has first and second terminals and an equivalent load impedance is connected to the secondary winding when viewed from the pulse transformer excluding an impedance of the secondary winding itself. A power source supplies a voltage, and a switching circuit supplies the voltage from the power source to the primary winding of the pulse transformer in a first mode and cuts off the supply of the voltage to the primary winding in a second mode in response to control signals. A short-circuiting part short-circuits the first and second terminals of the primary winding of the pulse transformer for a predetermined time from a time when the switching circuit assumes the second mode.

Constant voltage drive type driver circuit

Extended logical scale structure of a programmable logic array

A threshold value control system for discriminating an input signal received by a receiver circuit is provided having a mode setting unit for determining a mode setting signal corresponding to a connection pattern of the receiver circuit. A variable threshold generating unit generates a variable threshold which varies depending on the variation of the level of the input signal. A constant threshold value generating unit generates at least one constant threshold by which the level of the input signal can be discriminated even when its level cannot be distinguished by the variable threshold value. A threshold comparing unit compares the variable threshold and each of the at least one constant threshold to output a comparison result. A switching unit passes only one of the variable threshold and the at least one constant threshold as a discriminating threshold based on the mode setting signal output from the mode setting unit and the comparison result output from the threshold comparing unit, the discriminating threshold being sufficient to discriminate the digital level of the input signal. A comparing unit compares the level of the input signal and the discriminating threshold to output a discriminated result, therefore, bit errors or synchronization deviation can be prevented even when there is a superimposition of frame signals or noise.

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Chikushi, Japan

Hideki Shutou