This circuit from a 1967 documentation generates 2.5 Hz signals depending on the capacitors used, in this case 160 uF. For 4 6700 pF the signal will be 20 kHz.
The frequency of this astable multivibrator depends not only on the capacitors, but also on the...
This interesting sound effect circuit that produces the sound of bulls or Bull Horn was found in...
This 1967 Raytheon circuit uses an optical coupler of the era and has a range of 800 to 200 Hz....