This circuit for light modulated in frequency (FM) operating at 50 kHz was found in a 90’s Electronics Now. The circuit has an active filter. Modern equivalent transistors can be used.
This Linear Technology cold cathode fluorescent circuit operates on power from 4.5 V. The...
Circuits like this one, using the LM386 audio amplifier, are available from other sources in this...
This circuit was found in a Dutch documentation from 1970. The circuit makes use of semiconductors that...