This interesting circuit uses a sodion valve that we have already described in an article on the website. The circuit uses several batteries for power. The phone is of high impedance.
Using an optocoupler this circuit turns on the light in a bedroom for a set amount of time when...
This basic voltage comparator circuit has a reference voltage given by a zener diode. The input...
Found in a Hands On Electronics of the 80s, this circuit makes use of a gas sensor of the time....