Cable anti-theft alarm circuit

Shown is a cable burglar alarm circuit. The circuit
is simple and easy to make. When the cable is stolen, it can send out a continuous audible and visual alarm
signal.
    When using, twist the ends of the two empty wires in the cable together, and
then connect their beginning ends to the input terminals M and N of the alarm. When the
cable is broken, since the resistance of the cable is small + it is equivalent to
the base and emitter of the transistor VT being short-circuited, VT is cut off, and the relay K
does not close. When the cable is cut, VT conducts, the intermediate relay K closes, its normally open contact closes, the alarm HA and the warning light EL
light up at the same time, reminding the staff that the cable has been stolen.