This circuit was found in a Popular Electronics from the 90s. The transistors are general purpose, and the gain depends on the ratio between R2 and R1.
This circuit generates a tone of a bell and can be used in this type of application. The circuit is...
This circuit uses a common-cathode 7-segment display powered from a decoder and a 0-9 counter. The...
With this simple converter found in a 1997 documentation, it is possible to tune VHF stations to a...