Two sensors are used in this simple remote-control circuit, one to switch on and one to switch off the relay. The circuit is from 1986 documentation. The transformer has 12 V of secondary.
The figure shows how to implement an alarm buzzer in an LM3914 to warn about crossing the scale...
This circuit can act as a shield being controlled by a microcontroller by pin 1 or 2. The...
This circuit was obtained from a 1980's QST magazine. The circuit can generate 1 to 15 MHz signals...