线路通断检测器的设计：

1．用压电陶瓷蜂鸣片作为电声元件。

2．用两根导线作为测试探针

3．线路通断是通过测试电阻的大小来判断，有以下三种情况：

（1）若150Ω<Rx<900Ω，则蜂鸣片不发出声响。

（2）若Rx>900Ω或者Rx<150Ω，则蜂鸣片发出间歇式的滴－滴声响。

以上各临界阻值（150Ω和900Ω），允许误差±10％

4．＋15V直流稳压电源需要设计。

-Line-off detector design:

1. Piezoelectric ceramic buzzer as the electro-acoustic components.

2. As a test probe with two wires

3. Lines off by testing the resistance to determine the size, the following three conditions:

(1) If 150Ω <Rx <900Ω, the buzzer is not audible.

(2) If Rx> 900Ω or Rx <150Ω, then the buzzer sent intermittent drip- drip sound.

Above the critical resistance (150Ω and 900Ω), tolerance ± 10

4.+15 V DC power supply need to design.