**Details** This C1 device requires the Tibbit #00-3 to be installed in the neighboring ["M" Tibbit socket](http://docs.tibbo.com/phm/the_standard_tibbit_tile.htm). The LED is to be controlled through line A of Tibbit #00-3. Set the line LOW to turn the LED ON. **IMPORTANT NOTE!** Red and blue LEDs used in this Tibbit are high-brightness LEDs that are fairly visible in regular office lighting conditions. Green and yellow LEDs are less bright and are only recommended for use in dimly lit environments (equipment closets, etc.).