This circuit was obtained in a QST magazine from the 90s. The circuit makes use of components that are uncommon today. The circuit includes a gain selection switch.
This circuit controls a relay causing it to open and close its contacts at a speed that depends on the...
This circuit is from an Electronics World of 1968. The transistors are of the time and the power...
This circuit is from a Motorola manual from the 70s. The circuit can be implemented with more...