PURPOSE: To execute calibration simply in a short time with high accuracy by including incorporatedly an automatic calibration circuit for transmission/reception characteristic in a transceiver.

CONSTITUTION: When a calibration command is inputted to a terminal T3 of a receiver B at first, a calibration control circuit 4 changes over a signal changeover switch 1r to the position of calibration. A main current of the circuit 4 is transmitted to a transmitter A so as to drive a signal changeover switch 1t and switch the input of an amplifier circuit (b) to the position of a reference sinusoidal wave generating circuit 3. A prescribed amount of DC bias is superimposed on the output of the circuit 3 from a circuit e0, the result is transmitted to the receiver B and inputted to a DC component detecting circuit 5 and an AC component absoute value detection circuit 7 via the switch 1r. When the error of the DC bias of an analog transmission system exceeds a permissible error, the bias value of a variable bias circuit (j) is controlled via a bias control circuit 6. On the other hand, when the amplifier error of the analog transmission system exceeds the permissible error, the amplification factor of an amplifier circuit (h) is controlled via an amplification factor control circuit 8.