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.
This is a simple configuration for a low-pass filter using a 741 operational-amplifier. Other...
November 2016 - The TL3780 ultra-miniature E-switch touch switches can now be obtained from Mouser...
This circuit has been found in operational documentation of the 1970s. The circuit has a fail-safe...