Radio with amplifier (CB20486E)

We found this circuit in a publication of 1991. The audio amplifier is an operational that admits equivalent.

Flyback Tester (CB4644E)
Flybacks are no longer misused. However, if the reader wants to recover an old analog television...
Blown Fuse Alarm (CB4875E)
This 3V-only circuit was found in old American documentation, but can be implemented with...
455 kHz modulator with the 555 (CB7990E)
This circuit has a configuration that can be found elsewhere on this site. The power supply can...