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.

Precision Low Frequency 555 Oscillator (CB8088E)
Found in Electronics now, this circuit generates signals given by the formulas next to the...
5 A TTL power source LM340 (CB14256E)
This source was found in the National Semiconductor's Linear Applications Handbook of 1994....
Same Antenna for TV and FM (CB17479E)
This circuit is another practical idea for places where they still receive signals from analog TV. The...