Low battery indicator 555 (CB9551E)

This circuit can operate with different voltages, depending on the zener used. We found it in a 90s American documentation.

Neon Flasher (CB20941E)
This simple expandable circuit was obtained from a Popular Electronics from the 80's. The supply...
JFET Crystal oscillator III (CB19850E)
The frequency of the LC resonant circuit must be the same as that of the crystal and the JFET...
Pressure or Beat Sensor (CB11516E)
This circuit was obtained in a Popular Electronics of 1991. The magazine no longer exists, but the...