Found in an April 1977 Radio Electronics issue, this circuit uses the well-known XR2206. The C1 values for the various frequency bands are given next to the diagram.
Found in Motorola documentation from the 90s, this circuit makes use of a triac from that time. The...
This transistorized signal injector was one of the first that we found using the well-known...
This 200-mW amplifier uses one of the first commercial power transistors. The circuit is from a...