Included with IP Office R4.0 Standard Edition, the IP Office 500 system supports up to 32 telephones, with capacity for 16 analog trunks or 4 digital trunks (96 T1/PRI or 120 E1). Optionally, SIP trunks are also supported. With Professional Edition software, the IP Office 500 system supports 8 expansion modules providing for a combination of 270 analog, digital, and IP extensions. Additional analog trunks can be provisioned using the IP400 Analog Trunk 16 module.