This car battery monitor was featured in the January 1988 issue of Radio Electronics magazine. The circuit uses common transistors and has 3 levels of indication made with common LEDs.
The filter shown in the figure, using only an operational amplifier, is characterized by allowing 1...
Found in a 90s American documentation, this circuit can be used as a shield, just change the...
Found in a Philips' 1968 documentation, this circuit is slightly different from the previous one. The...