PURPOSE: To obtain a transmission line interface circuit for burst type bidirectional transmission which can prevent the tails caused continuously in a transmitted transmission waveform and then shorten the guard time in more simpler configuration.

CONSTITUTION: A control signal 15 is set at a high level right after a transmission signal 13 is set at a low level, and a switch 6 is close so that a wiring 10 connected to a reception circuit is short-circuited. In such a configuration, the energy remaining at a transformer 8 after the end of transmission is forcibly discharged. Thus the level of the remaining energy is rapidly attenuated. Then it is possible to prevent the tails produced continuously in a transmitted transmission waveform and also to shorten the guard time.