TERMINAL DEVICE PROVIDED WITH ANALOG SWITCH CIRCUIT

PURPOSE:To connect a terminal device to a telephone line without giving effect on any insulation test by providing a switch disconnecting the terminal device from the telephone line and a timer circuit when it is judged that the insulation test is performed. CONSTITUTION:When the insulation test is performed at 200V, a high-voltage analog switch 2 is interrupted, and when the test is conducted at 35V, a low voltage analog switch is brought into the interrupting state. When the insulation test is performed at 48V, the analog switches 2, 4 are brought into the conducting state, a terminal device 5 outputs a release signal 7 because no call signal comes from a central device so as to interrupt the switch 2. When a DC resistance value of the telephone line is very large by the manual insulation test, since drive power to the terminal device 5 is very small, it is detected by a timer circuit 6 operated at very minute power consumption, a release signal 10 is generated so as to bring the switch 2 to the interrupting state.