Found in a 1970 American publication, this circuit uses transistors of the time. These transistors may be replaced by current equivalents. The factor Q is greater than 3 000.
This circuit for VCR recording heads was found in the February 1990 issue of Radio Electronics magazine....
This very simple continuity tester uses a small 1.5 V lamp (type used in flashlights). Can be...
This commercial radio with 3 earphone listening transistors was manufactured in Japan in the...