DirectOutput Framework R3++, Grand Unified Edition
DirectOutput is an add-in for Visual Pinball and other programs that provides software control over external feedback devices in a virtual pinball cabinet.
Feedback devices are things like lights, beacons, solenoids, shaker motors, and gear motors that augment the "video game" action with audio, visual, and tactile effects. These feedback devices are physically connected to the PC through an "output controller", typically a USB device. A variety of output controllers are in common use, including LedWiz, PacLed, SainSmart USB relay boards, and open-source systems such as Pinscape.
DOF acts as a hardware virtualization layer: it provides a common interface to the different hardware devices so that the pinball simulator software doesn't have to speak 10 different USB protocols. DOF also handles all details of effects timing and device state management, so that the pinball simulator doesn't have to know anything about the physical devices; it merely sends DOF data on the abstract game events, and DOF takes care of mapping the game events to device effects, mapping the device effects to hardware states that evolve over time, and mapping the hardware states to the output controller protocol commands necessary to effect same.
DOF documentation can be found at http://directoutput.github.io/DirectOutput/
This is the mjr "Grand Unified" edition of DOF, which merges all of the known forks as of January 2018. Several forks with different add-on features have emerged since the last official DOF release from SwissLizard in December 2015. This edition is an attempt to re-unify all of this work under a single version so that users don't have to pick subsets of available features - just pick this version and you'll have them all.