This circuit also appears elsewhere on this site, obtained from other sources. This is an 80's American schematic book. Instead the lamp can be used white high-brightness LEDs.
We found this circuit in an English documentation from the 60s. The integrated circuits are the...
This circuit was found in a 90s Popular Electronics. It generates tones given by the oscillators and...
This amplifier circuit applies its signal to an ordinary audio amplifier to pick up signals from a...