Musical Touch Bell UM66

This musical call bell circuit can be operated by just bridging the gap between the touchplates with one’s fingertips. Thus there is no need for a mechanical ‘on’/‘off’ switch because the touch-plates act as a switch. Other features include low cost and low power consumption. The bell can work on 1.5V or 3V, using one or two pencil cells, and can be used in homes and offices. Two transistors are used for sensing the finger touch and switching on a melody IC. Transistor BC148 is npn type while transistor BC558 is pnp type. The emitter of transistor BC148 is shorted to the ground, while that of transistor BC558 is connected to the positive terminal.

click for large image

Musical Touch Bell UM66