| 摘要 |
PURPOSE:To eliminate the need for an AC oscillating circuit, by inverting the polarity of a current supplied to a telephone set at calling in a subscriber telephone set, and energizing a DC drive buzzer. CONSTITUTION:A diode 34 and a DC drive realy 35 are connected in series in the telephone set 3, and contacts rl2-1, rl2-2 of a call relay 46 are connected to subscriber lines W1, W2 through changeover to apply a voltage of inverted polarity from DC power supplies 44 and 45. Thus, in the telephone set 3, a current i2 of reverse direction flows, the buzzer 35 is energized to generate a call tone. |
