This receiver was found in a 1924 book by Gernsback. The circuit uses three tubes and is powered by 3 batteries of different voltages, common at the time.
This small crystal microphone transmitter was indicated in an 80s spy book. The range depends on...
This circuit, found in a 1978 publication, converts 5 V into a symmetrical 15 V output under low...
The configuration shown in the figure is one of the most traditional when it is desired to produce...