The Excel 500 System is part of the EXCEL 5000 family of controllers. The Excel 500 housing has four slots for plug-in modules. The primary unit consists of a CPU module (Excel 500 uses XC5010C for special high-performance requirements or XC5210C), a power supply module (XP502), and two additional I/O modules. Up to four more Excel 500 housings (without CPU and Power Supply module) can be connected in series providing slots for additional modules. The Excel 500 controller has a LonWorks® bus interface, allowing interoperability with a wide range of Honeywell and third-party controllers and devices. Up to 512 LonWorks network variables can be mapped to data points.