This circuit is from a Motorola documentation from 1968. The integrated one is an operational of the time still in metallic casing. Modern equivalents can be used.
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...