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, suggested by National Semiconductor, provides an output voltage proportional to the...
This powerful alarm circuit was found in the July 1975 issue of Radio Electronics magazine. The...
This two-transistor circuit was found in the January 1994 issue of Electronics Now magazine....