This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
The integrated circuit used in this amplifier is not common today. The power can be between 4 and...
This circuit was obtained from a 1997 publication. It is an alarm that has a lock and a bistable...
We found this circuit in a 1991 publication. What it does is to amplify a signal with unit gain...