This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals with 1 Vpp at 50 ohms load. Used transistors are still common today.
This set-rest relay uses two SCR and two switches to control a DC relay. The circuit can be used...
This control panel allows the use of NO and NC sensors, turning the alarm on after 30 seconds...
This circuit, from the 1990 Motorola Dataar Databook, can use any LM139 series comparator. The circuit...