The MRC stationary accessory decoder comes with 4 pairs of outputs. Think of it as 4 decoders in 1, each having its own sub-address. This decoder is an NMRA compatible accessory decoder. You must use DCC systems that support CV programming and have accessory decoder function capability, such as Prodigy Advance, Prodigy Advance2, Prodigy Wireless, and Prodigy Express (when used with the Prodigy Advance handheld). Can be used with slow motion or twin coil switch machines, trackside signals and builiding lighting. Complies with Part 15 of FCC regulations.