This circuit, to control air conditioning systems, was found in July 1984 Radio Electronics magazine. The circuit is for old types of the time that did not have microcontroller control.
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...