This circuit identifies the polarity of DC signals and if the signal is AC. The circuit is from 1969 US EDN documentation. Operational may be equivalent.
This interesting automotive alarm was found in a 90's Popular Electronics. The circuit uses...
Using the 4001 integrated circuit, this latching relay can employ any general-purpose transistor. The...
The PA222 integrated circuit used in this project from an American 1967 documentation is not...