Found in a QST magazine from the 90s, this circuit broadcasts on different amateur radio bands depending on the coil. Data for the coil and crystal are provided next to the diagram.
This control for 12 V drills was found in a 90s Elektor. The components are current, and Q1 can be...
Found in an old English publication, this circuit applies to the 240 V network, but can be changed to...
This circuit was found in a 90s Popular Electronics. With it, using a 4066, it is possible to...