Multi-channel disconnection alarm circuit

Circuit working principle: Normally, the trigger terminal of each thyristor is connected to the negative pole of
the power supply through a hidden wire, and the thyristors are in a cut-off state. The oscillation alarm circuit composed of VT1, VT2, C1,
C2, R1 and the speaker does not work because it does not receive power , and
the light-emitting diode does not light up. Once a hidden thin wire is pulled off, the corresponding thyristor will be
turned on, the alarm will sound, and the LED in that path will light up, informing the security personnel that something went wrong
. To disarm the alarm, just press the switch.