We found this version of the automotive tachometer in a 1980s publication. Variations from other sources appear elsewhere in this section. The indicator is a 0 to 1 mA milliammeter.
The different aspect of this source is the use of a 12 V lamp as a current regulator together with a...
This shield circuit was found in an American publication from the 80's. The triac is of low...
We find this circuit in a 1970 publication. Transistors can be replaced by current equivalents and LDR is...