This 1 to 40 MHz amplifier is from a 1969 Motorola documentation. The components are of the time but admit modern equivalents.
This additional bell circuit was found in the February 1994 Electronics Now magazine. The...
A delay of a few seconds to a few tens of seconds can be achieved with this circuit found in a...
This circuit uses a transistor to trigger the alarm from a low quiescent current sensor. The relay...