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.

Geiger Radiation Detector (CB18334E)
This circuit is from a Japanese publication in 1967. The circuit uses a Geiger-Muller valve and...
Tachymeter (CB19871E)
Motorola's LM13600 integrated circuit is not very common today. The input voltage is 10 mV. We...
LM382 Preamplifier (CB19616E)
This circuit is from a 70s linear integrated manual. The integrated circuit used is uncommon today...