The circuit shown was found in American documentation from the 1990s. The transistor can be of any general-purpose type.
This circuit was found in a 1995 documentation. Its purpose is to indicate voltage levels that are...
This circuit can test quartz crystals from 3.5 to 90 MHz. Its supply can be made with voltages from 8...
We have here a very interesting project found in a 1982 publication. By the operation of the...