This audible continuity test was obtained in a book from the 90's describing simple projects. The feeding is done with a single battery.
This amplifier stage was found in a 1956 Sylvania manual and has an unusual configuration with a...
In the circuit shown by figure 1, a10 mV AC signal applied to the input produces a 1 V signal in...
This circuit was obtained in 1974. It serves to indicate the tuning of stations on a common...