This low frequency sinusoidal oscillator was obtained in documentation from the 1970s. Operational equivalents can be used. The FET is a general-purpose type.
This circuit uses a 555 (according to the diagram) to generate 50 ms tone bursts at a frequency of 1.5...
This grounding test circuit was found in an American 80's documentation. The circuit is for the...
This circuit allows frequencies between 1.8 and 30 MHz to pass. Data for the coils is provided next to...