This 800 Hz sinusoidal oscillator was found in a 1970s American documentation. The transistor supports a modern general-purpose equivalent. The frequency is given by the RC network that can be changed.
This circuit, which in our times would be called a shield, can also be used with other loads. The...
This circuit is from an old American documentation from the 70s. Transistor 2N3904 can be replaced by...
This application of the 555 was found in the November 1992 Radio Electronics magazine. The...