Found in the May 1971 Radio Electronics magazine, this is the circuit for a commercial high-impedance instrument. The circuit uses 4 transistors and is powered by 2 9 V batteries.
This 200 kHz oscillator was found on a 90's EDN. It consumes only 2.8 mW and has CMOS compatible...
Although we found this circuit in an old documentation from the 70's it can still be assembled with TTL...
This audible continuity test was obtained in a book from the 90's describing simple projects. The...