Virtually any FET can be used on this voltmeter found in old documentation. The indicator is a microamper meter 0-100 uA and the accuracy of the circuit depends on the accuracy of the resistors used.
Found in a 1964 CQ magazine this circuit consists of an automatic telegraphic key, providing the...
Found in a 1967 American electronics magazine, this circuit has an input impedance of 2000 ohms....
This circuit can generate signals from 80 to 800 Hz with an amplitude of 0.3 V. We find it in a...