A single customer purchased a complete RailPro system. After working with it for a couple of weeks he decided to go with another system. These CB-1s are  like-new WITH manual and packaging. They have had very limited use. A great opportunity to save serious money!
 
The CB-1 is used to divide the output of a power supply to isolate small sections of track, limiting the impact of short circuits if derailments occur to just one area of your layout. Add multiple CB-1 to isolate several sections of track.
 
Additional information here: https://www.ringengineering.com/CB-1.htm