This circuit is from a documentation from the 70s. The circuit uses logic gates of the time, which in many cases were arrays of transistors allowing use as audio amplifiers, as in this case.
This interesting control circuit was found in an Electronics Now from 1988. Through it we can...
This circuit causes neon lamps to flash randomly from a low voltage supply (1.5 to 3 V). The...
Any operational amplifier, like the 741, can be used on this oscillator whose frequency depends on R1...