PURPOSE: To prevent a troublesome operation such as the manual temporary opening and recapturing operation of a telephone line when the time-out of a telephone switchboard occurs.

CONSTITUTION: When a telephone line capturing circuit 13 captures a telephone line 12, a telephone circuit capturing time detecting circuit 15 starts to count the capturing time. When the capturing time count value is beyond 20 seconds being a time just before the time-out of a telephone switchboard 11, a telephone circuit temporary opening circuit 14 opens the telephone circuit 12 for only one second, and the telephone circuit capturing circuit 13 recaptures the telephone line 12. The above mentioned operation is repeated until a dial operation is performed. When the dial key of an operating key group 18 is depressed, a control part 17 controls a dial circuit 16 in order to transmit a dial signal to the telephone line 12.