| 摘要 |
<p>PURPOSE:To directly call out arbitrary slave telephone unit, by detecting the continuing time of selected call signal in two waves parallelly received, designating the slave telephone set with this time length and calling the slave telephone set when the tone signal is received. CONSTITUTION:The signal detection circuit 19 identifies the call of the reception stand (master telephone set) 7 and the slave telephone set 9 and feeds the call signal to the respective slave telephone set 9. The call of the reception stand 7 is made with the combination of series signal for the first, second and third waves, and the combination signal is fed from the master station. For example, after the reception of f1, f2 among the frequencies f1, f2 and f3 simultaneously for about t1 seconds, when the signal of f1 and f3 is received at the same time, the reception stand 7 is called and the output 20 is outputted. Further, in case of call out of the slave telephone set 9, the slave telephone set is selected with the reception time length in f2 and the output 21 is outputted when f1, f2 are received at the same time and the output is kept.</p> |
