This circuit is from an American 80's documentation. The circuit indicates when the voltage of a 9 V battery drops below 7 V. The transistors can be BC548.
We found this circuit in the Texas Instruments' Linear Circuits Applications. It uses an...
The integrated circuit of this pulse generator is 4093 and the frequency can be between a fraction of...
This circuit was found in the November 1989 Radio Electronics magazine. Power supply depends on...