PURPOSE: To easily attain the amplification of a bidirectional calling signal by providing a circuit passing only a DC component, an AC amplifier and a changeover circuit switching the AC amplifier to be bypassed so as to connect it to a telephone line directly.
CONSTITUTION: In turning off a switch 25, the output of an inverter 24 goes to an L level, a transistor (TR) 23 is turned on, since no current is conducted to a relay 22, contacts 141∼144 ar in the state as shown in figure, and a telephone line and a telephone terminal are connected via a bypass circuit 15. In turning on the switch 25, the output of the inverter 24 goes to an H level, a TR 23 is turned on, a current is conducted to the relay 22 by a voltage +V, the contacts 141∼144 are connected switchingly, and the telephone line and the telephone terminal equipment are connected via AC amplifiers 11, 12. Then the DC components such as a DC loop signal, a dial pulse signal and a call signal or the like are conducted through a choke coil 3, and are sent as they are, and the bidirectional calling signal is amplified and outputted respectively.
KOIKE JUNICHI
SUGIMOTO NORIYA
HASEGAWA DENKI SEISAKUSHO
| JPS5211167A | 1977-01-27 | |||
| JPS4866705A | 1973-09-12 |