We found this cable tester in a Popular Electronics from the 90s. The circuit uses a connector according to the cable to be tested. Adaptations can be made for different types of cables.
We found this circuit in a 1967 Electronics World. The circuit can be designed to control other...
The presented circuit monitors a line indicating if it is busy if there is an extension. The...
This circuit is from old documentation. The operational amplifier is uncommon nowadays. The...