| 摘要 |
PURPOSE:To prevent received electric power from decreasing greatly even when a telephone set circuit is connected to another telephone set by branching and used by providing a transmitting amplifier circuit which varies in DC characteristics at a specific circuit terminal voltage as an inflection point. CONSTITUTION:The 1st transmitting amplifier circuit 3 and the 2nd transmitting amplifier circuit 8 are connected to circuit terminals 2a and 2b in parallel to each other. The 1st transmitting amplifier circuit 3 is constituted similarly to a conventional circuit. The 2nd transmitting amplifier circuit 8, on the other hand, consists of a transistor (TR) 81 for voltage-current conversion and a bias resistance 82. The DC characteristics are controlled by the 2nd transmitting amplifier circuit 8 below EL=4.8V. The DC characteristics of the telephone set circuit, therefore, have two different characteristics about P3 as the inflection point. When a normal telephone set is branch-connected to this telephone set, DC electric power PF supplied to the electronic telephone st is larger than PC=1mA of the conventional circuit. |
