This circuit is used to detect PLL signals from the 4046 IC. The circuit is from an Electronics Now from October 1994. The indication is made through LEDs.
The amount of light emitted by na LED is given by the intensity of the current flowing across it....
When the vehicle door is closed, this circuit keeps the internal lights on for a time depending on C1....
This circuit was found in an old documentation from 1968. The voltage gain is 70 and the...