Found in an English publication from the 1980s, this circuit can be built with equivalent transistors such as the BC549. The signal must be applied to an external amplifier.
This circuit makes use of a specific 80's component and was found in an American manual of the...
The circuit shown in the figure, generates a positive pulse whose duration depends on C1, from the...
We found this circuit on the internet. The components are current, and the time depends on C1...