This 1968 documentation circuit uses a relay to control loads up to 1 kW (depends on relay contacts). The supply voltage depends on the relay.
We find this circuit in a 2005 Linear Technology manual. The circuit applies to small DC motors...
This 12V battery charging circuit automatically shuts off at the end of the charge. The disconnect...
This is one of many Morse code audio oscillators that can be found in this section. The circuit...