This circuit was found in Motorola documentation from 1966. The lamps are according to power and current according to the components used which are uncommon today.
The circuit presented is based on a mechanical tuning fork. The circuit is suggested by National...
This source, from a 1982 documentation, uses a triac to control the power and voltage applied to...
This circuit was found in a 1990 Electronics World magazine. The circuit can be mounted today by...