This circuit is from the 80's but uses common components today. The relay is voltage sensitive according to the power supply used. Transistors may be general purpose types.
This is a Philips commercial circuit from the 90s. The integrated circuit must have a good heat...
This high-power circuit was found in July 1986, Radio Electronics magazine, requiring a...
This circuit was found in a 1967 US documentation. The FET is general purpose and the 6V zener....