This analog frequency meter for low frequencies was found in Radio Electronics magazine from July 1958. The circuit has several scales with the frequencies indicated in the diagram.
Published in 1988 in Hands-On Electronics, this circuit converts the 12 V of a battery into 120 V...
This photoelectric circuit from a 1960 publication uses a 6.3 V electromechanical counter, common at...
This circuit consists in a capacitor bridge for capacitance measurements. The circuit can be...