This simple audio and RF signal tracker was found in a Japanese publication in 1967. The transistors are made of germanium and the headphone is made of crystal.
We found this circuit in a 1964 Electronic Design. It provides 0.5 V signals from 4 kHz...
This circuit is from a 1977 application manual for timers. The circuit provides a negative pulse...
With the precision given by the crystal this circuit provides signals of several frequencies for the...