This frequency divider by 10 uses discrete components only. Modern equivalent components can be used as the circuit is from an 80's documentation. Nearby frequencies can be used.
Found in a 90s 73 magazine, this circuit uses an unusual component today which is the XR2206. |...
This random noise or white noise generator was published in Radio Electronics magazine in July...
This circuit was found in Philips documentation from 1967. The phototransistor is from that time,...