This circuit generates signals in the range of 50 kHz to 1 MHz with a rectangular waveform. The circuit is from an English publication from 1980. The transistors can be BC548 or 2N2222. The capacitors must be ceramic, and the power supply can be from 9 to 12 V. The C1 capacitor must be obtained experimentally in the range of 1nF to 10nF.
