PURPOSE: To prevent missing speech head and tail of conversation by designing the titled circuit that the transmission loss of other signal line is decreased stepwise when the transmission loss of one signal line is increased stepwise in the hang-over state of the transition between the transmission and reception state.
CONSTITUTION: A comparator circuit 13 brings an output to logical H when a transmission signal level is larger than a reception signal level and brings the output level logical L when the relation of the signal level is reverse. Time constant circuits 14a∼14c consist respectively of diodes Da∼Dc blocking the output signal of the comparator circuit 13, charging resistors R1a∼R1c connected in series with the cathode of the diodes Da∼Dc, capacitors Ca∼Cc charged via the charging resistors R1a∼R1c by the output of the comparator 13 and discharge resistors R2a∼R2c connected in parallel with the capacitors Ca∼Cc. The discharge time constant is set longer for the time constant circuits 14a∼14c having a shorter charging time constant. Thus, the transmission/reception is attained at the same time in the hangover state and no howling takes place.
FUKAGAWA HITOSHI
TAKEHARA KIYOTAKA
KINEKAWA YASUKAZU
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