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.
This circuit, from the 90's, is intended for operation with vinyl record players of the time, as...
Using a zener diode it is possible to change the linearity of the scale of an analog instrument by...
Found in American documentation from the 1980s, this circuit prolongs the ringing of a doorbell or chime...