We found this time base of 0.1 to 90 seconds in a circuit manual from the 90s. The single-use transistors used are common and the frequencies given by the adjustment by the potentiometer.
This circuit uses a crystal phone and can be built with more modern transistors like the BC548. The...
The resistors in this circuit marked with * must be within 1% tolerance. The circuit is from the...
The existence of field effect transistors at the input of the integrated circuit (operational...