The Plus option lets the Plan B automatically switch to a live secondary program source (phone line, STL, ISDN codec, off-air receiver, etc.) in the event of a main program source failure. If both live program sources have failed, the Plan B will activate its internal audio source until either live feed returns. The Plan B Plus always maintains the proper program source priority, automatically putting the highest-priority available feed to air.

All switching is passive, and any source can be monitored or forced to air remotely via the built in voice remote control or via an Internet or network connection. The Plus option is an additional circuit board installed inside the Plan B’s chassis. It can be retrofit in the field by technical personnel, allowing an existing Plan B to be upgraded to a Plan B Classic Plus.