This two-tube circuit, one being a double, was found in Radio Electronics magazine from July 1958. The distance to the microphone depends on noise and losses. The cable must be shielded.
This electronic flash circuit was found in the March 1961 Radio Electronics magazine. The circuit...
Like the previous circuit, this is used in the analog part of the telephone lines. The same...
This circuit was found in documentation from the 90s, being indicated for use with tape recorders given...