This circuit was found in the February 1985 issue of Radio Electronics magazine. It is based on an AY-3-1350 melody generator that was common at the time. It is suitable for analog lines only.
This receiver for the mid-wave band was found in a documentation from the 60's. The transistors are made...
In the figure we have a symmetrical power supply stabilized by a zener diode. Transformer and...
This circuit is a digitally controlled variable capacitor. We found it in American documentation from...