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 circuit is from a publication from the 70s. The operational amplifier is from the period. Modern...
We found this circuit in the October 1992 issue of Radio Electronics magazine. The duty cycle can...
This circuit digitally counts input pulses. The circuit from a November 1970 Radio Electronics uses...