This longwave signal booster circuit was found in the 1995 Encyclopedia of Electronic Circuits Volume 5. Note the dimensions of the board. The transistor is a general-purpose transistor.
Another of the many tachometer circuits we have on our site. This one is from the September 1976...
More and more supercapacitors are being used as supplementary sources of energy in several...
We find this circuit in a 555 application manual. The circuit generates triangular signals that...