We found this circuit in a 1973 documentation. The null adjustment trimpot is 10k. The circuit can be powered by symmetrical sources from 9 V. The diodes on the bridge can be 1N4148.
Found in old documentation, this meter has a high voltage inverter for the Geiger tube. The...
In the figure we have a 100 kHz crystal-controlled oscillator using an operational amplifier....
Found in the November 1974 issue of Radio Electronics magazine, this circuit has a frequency range...