Found in an Electronics Now from the 90s, this circuit uses components that are still common. The LM3900 is a transconductance operational amplifier.
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....