555 multi-purpose car alarm circuit

Binary password  lock control type Alarm

Door lock reminder alarm with time sensor

Emergency sound and light alarm to inform power shutdown(optocoupler- audio oscillator)

Flame alarm

Fridge door open reminder

Improved sound and light alarm circuit with reverse switch

Life abnormal alarm

Light controlled alarm to secure from robbery

Light sensor alarm

Modular security system

News flash ring circuit or traffic alert alarm circuit

Photoelectric alarm switch

Second Power line carrier alarm

Solar water heater circuit