This circuit was found in an article in Electronics Now magazine from March 1997. The transistors are general purpose, and the indicator is a 1 mA full scale analog type.
The circuits shown below consist of diode protections against accidental polarity reversal in the supply...
Found elsewhere in this section, this circuit mimics the noise of a steam locomotive. This was...
In the original application of this circuit, from a 1985 documentation, we have only two entries....