This circuit was found in an old documentation for radio amateurs. The circuit makes use of an uncommon integrated today. The circuit converts telegraph signals to be used on the computer.
This circuit was published in an English magazine from 1980. The magazine no longer exists, but...
Found in a 1990s Motorola documentation, this high voltage circuit uses a PUT that is not a common...
This proximity sensor was found in a 90s Popular Electronics. The base is a PLL567 that operates...