This timer, like the previous circuits, uses a currently uncommon integrated circuit. The time is given by capacitor C1 and R2 which has the range of values indicated in the diagram.
This small audio amplifier of a few watts found in television sets was published in the magazine Radio...
This circuit monitors a common analog telephone line indicated for its use through LEDs. The...
This circuit activates a machine to dry hands (fan and heater) when the sensor detects the...