This receiver uses old transistors that are equivalent to BC548 and BC558. The photo diode is of any type. The receiver can be used on a highly sensitive audio link.
This SCR circuit, which can also be used for signaling places, was found in old American...
This former temperature sensor with a mercury sensor was found in a General Electric documentation from...
We found this parallel regulator in a 1973 publication. Transistors admit equivalents and the...