We found this circuit in the May 1996 Electronics Now magazine. The relay must have a voltage according to the circuit power supply and a trigger current of no more than 50 mA.
In the figure we have a typical constant current source circuit. Transistor can be equivalent as...
The circuit shown here uses a 4047 to produce three signals whose frequencies are determined by C...
The CA3020 integrated circuit was one of the first commercial types, sold in the 1960s. The...