Detailed Description

Small audio optocoupler is about the size of a pencil eraser and has 4 leads. These are found extensively in audio compressors, guitar tremolos, guitar amplifiers, music effect boxes, audio limiters, audio level controls, etc. Inside the black epoxy case is a 2 lead CDS cell (not a phototransistor, photodiode). The LED requires about 10 to 16mA current and the CDS cell varies from 150K resistance up to Megohms when no current is going to LED (off). When the LED has current flowing, the resistance is typically less than 400 Ohms. Dot on case marks cathode (-) if LED. Sold in a package of 5.