This circuit is from a 1980s Motorola documentation. The circuit can be made with modern equivalent components. The original circuit is for the 115 Vac (110 V) grid and has two settings.
This Popular Electronics circuit can be found in various versions on this site and in this...
This circuit is from the 1990 Motorola Data Databook. The circuit can be implemented with...
Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime...