Object detection alarm circuit with locking function

Object detection alarm circuit with locking function

Shown is an object detection and alarm circuit with locking function , which can be used for anti-theft alarm. If someone invades the photoelectric detection
space, the light is blocked, the photosensitive transistor is cut off, and its collector voltage rises, causing both Di and VT1 to conduct, the thyristor is also triggered to conduct, and
the alarm light emits light. Only switch Kl can be turned off . After a while, the alarm state can be released.