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 was obtained from an American 80's documentation. The balanced mixer can be shown in...
This circuit produces a square wave signal with the frequency determinated by R1 and C1. The upper limit...
In the figure we have the circuit of an amplifier for alternating signals with 10 times gain,...