Found in Unitrode documentation from the 1980s, this circuit makes use of PUTs, currently common components. The circuit must be powered with voltages around 15 V.
Nothing more useful on the bench than a variable voltage source. This is the source we found in...
Equivalent transistors can be used on this 80's circuit. Any general purpose PNP transistor can work...
This 1998 circuit controls the volume in a stereo system by touching switches. The circuit is for...