With the help of a quad opamp, a bi-color LED and a few passive components you can quickly build a simple signal level meter which has three detection levels.
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In Elektor’s October 2014 edition I spotted an article on page 28 describing a dot-display- driver [1]. This circuit reminded me of a design that I have used for decades whenever the need arises. The first occasion for this design was an existing device to which different type of microphones were to be connected. Despite the different sensitivities of the various microphones the levels of the output signals had to be always the same. This piece of equipment had naturally no spare space available for additional meters to allow the correct signal level to be set, but there was sufficient space however to accommodate a (bi-color) LED.