This circuit reproduces the dial noise in a small speaker. The transistor can be a general-purpose type. We found it in an 80's Electronic Design.
This circuit is from an 80's electronic component manual. It has the way to simulate an inductor...
This 1967 Electronics World circuit is suitable for frequencies up to 1 MHz. The setting applies...
This simple photometer was found in a 1977 Radio Shack manual. The sensor is a photocell, which can...