TELEPHONE TYPE TERMINAL DEVICE

摘要

PURPOSE:To make it possible to connect a multiple number of terminals to a same telephone line and to utilize effectively a telephone line by on-off controlling a switching means in proportion to the output of a voltage comparator. CONSTITUTION:Either the lifting of a handset 2 or the key operation of an on-hook dial makes a hook switching circuit 14 on and a voltage is supplied to a telephone line 13, and also a telephone line voltage Vr and a reference VR are compared at a voltage comparator 18. Since the voltage of the telephone line is lowered under the normal level when a telephone line 11 is in use, an output signal (c) becomes equal to L and a telephone circuit 1 is not connected to the telephone line 11 due to the OFF condition of a switching transistor 15.