Low battery indicator (CB9133E)

This circuit was found in Maxim's documentation from the 80's. The integrated circuit is from that time, uncommon today.

Digitally controlled audio switch (CB12748E)
This circuit can serve as a basis for a digital mixer or simply for a noiseless switch of audio...
Microphone mixer (CB7988E)
This traditional mixer configuration with a high input impedance was found in a 90’s Popular...
1-transistor radio (CB20247E)
This medium wave radio works with any general purpose NPN transistor. The diode must be made of...