Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
Instead of the lamps, LEDs can be used in series with 470 ohm resistors. The circuit is from an...
This interesting circuit that generates delayed pulses was found in the September 1992 issue of...
The circuit is from an old American publication. We can mount it with the BC548 and TIP31. The...