We found this circuit in a 1987 documentation. It is a multi-tester with neon lamp and LEDs operating with both low continuous voltage and high alternating voltage.
In the original version of this 1987 circuit, the loads are lamps, but it can be adapted to drive a...
We found this circuit in a Radio Electronics from the 90s. Transistors admit current equivalents,...
This CMOS frequency meter can measure frequencies up to about 1 MHz with a 3-digit resolution. The circuit is...