Found in an 1868 Mullard documentation this circuit has a dynamic range of 10 Hz to 25,000 Hz. Modern equivalent transistors can be used.
We found this circuit in a 1964 Electronic Design. It divides the frequency of a 20 MHz signal by...
This circuit was found in the November 1987 Radio Electronics magazine. The trigger voltage is...
This high-powered megaphone circuit is from a Radio Electronics from December 1964. Note the use...