sentences:  1 Crossbar system consolidated maintenance and testing activities into a single area of the central office, sometimes known as the MTC or "Maintenance Test Center".Whereas earlier systems, such as the panel switch had maintenance facilities spread throughout the office, it was found desirable to centralize these processes into a single space so that technicians could work more effectively.This decision was also driven by the use of markers, which carried out their individual tasks quickly, and interfaced with several other circuits while doing so.