This is the SB5 Smart Booster 5-Amp System w/Power Supply Model Train Power Supply Transformer by NCE Corporation.
Add an SB5 Smart Booster (command station / power booster) to your Power Cab when you need more track power. The SB5 can supply 5 Amps of track power while freeing up your Power Cab for true walk around control. The SB5 accomodates up to 6 throttles plus an additional 3 cab bus accessories such as AIU, USB or Mini-panels. An internationally approved 12/13.8 volt 5 Amp power supply is included.