Found in a 80s American documentation, this circuit pulses a lamp for optical relay tests. The circuit can be modified to trigger a high brightness white LED.
This analog tachometer was found in Radio Electronics from the 90s. The components used can still...
Found in an English Maplin documentation from 1983, this circuit generates separate frequency...
Found in a Philips documentation from 1968, this circuit detects the trimpot set input voltage....