The Mitel SX-200 MX Controller has the processing, memory, mass storage, power, and input/output capabilities to support up to 248 IP phones or 672 ONS / DNIC phones, or a combined total of 672 phones.

MX Controller
The Mitel SX-200 Integrated Communications Platform (ICP) provides the reliability and comprehensive features of a PBX, the ease of use and cost effectiveness of a key system, and the productivity-enhancing applications and networking efficiency IP communications. The SX-200 ICP allows you to implement the system you need today, whether this is with traditional or IP Telephony, with the option to add capacity and functionality as your business requirements change. It can be configured as an IP system, TDM system or any combination of IP and TDM. The choice is yours. The configuration is simple.
Six LS / CLASS circuits; upgradeable to 12
Two analog station circuits; upgradeable to four
Two DNIC circuits
Four ports of voice mail; upgradeable to 24
Up to 748 mail boxes
Support for four FIM connected to SX-200 peripheral cabinets
Support for seven CIM connected to SX-200 peripheral cabinets
Support for 672 TDM ports (7 peripheral cabinets)
Support for four embedded digital links (T1 / D4)
Eight digital links for T1 or PRI connections
248 IP phones
24 IP trunking channels
Front Panel
Dry Contacts for Alarm, Door Relay, and Auxiliary Ringer
Two RS-232 ports for Printer and Maintenance terminal
Two onboard CIM (Copper Interface Module) ports to connect Peripheral cabinets, ASUs, NSUs, and PRI cards.
One 10/100 Ethernet connection
Expansion sites for MMC modules (T1/E1 Framer, Quad CIM, Dual FIM, Dual and Quad DSP)
CompactFlash card reader for performing software upgrades
Status LEDs.

Rear Panel
Power connector
Protective ground to ground the chassis
Music on Hold port
Paging equipment connector
Amphenol Connector for analog trunks and ONS/DNIC stations

SX-200 ELx Peripheral Cabinet
SX-200 ELx peripheral Cabinets are supported on the SX-200 ICP MX only. Up to seven cabinets can be connected to the controller via CIM or FIM cables. The SX-200 ELx peripheral cabinet can be mounted in a standard 19" rack, or stacked. The control cabinet and the peripheral bays are linked by fibre or copper cables. Located on the rear of the SX-200 ELx cabinet are nine connectors, a printer port, a grounding connector, and a maintenance port.