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.
This preamplifier appears elsewhere in this section and this version was found in American...
This 2000 circuit, found in the documentation of the time, is intended for charging this type of...
Based on the well-known LM3909, this LED pulser circuit was found in American documentation from...