This circuit was found in the July 1992 Radio Electronics magazine. Sensitivity adjustment is made at R6. Supply voltage is matched to that of the relay.
This circuit is from a 1967 General Electric SCR manual. Modern equivalent SCRs can be used. The...
Taken from a 1954 book by Rufus Turner, this amplifying step with PT2A transistors provides an...
This symmetrical power supply uses only one zener diode in its regulation, supplying voltages of...