Electronic Circuits and Software Related Photocell Activated Toys These circuits use a CdS photocell to simulate motion detection, by sensing shadows and other small disturbances in ambient lighting caused by nearby Watch-Dog for Telephones These devices provide blinking or beeping type line-tap/misuse indications. Quite often they do not offer guaranteed protection against unauthor-ised Factory Siren This circuit produces a sound similar to a factory siren.It makes use of a 555 timer Ic used as an astable multivibrator of a center frequency of abou Police Siren circuit This circuit produces a sound similar to the police siren. It makes use of two 555 timer ICs used as astable multivibrators. The frequency is controll Light-sensitive Alarm The circuit detects a sudden shadow falling on the light-sensor and sounds the bleeper when this happens. The circuit will not respond to gradual chan
