Four SIP trunks

A minimum of four IP (SIP) trunks are required due to the NEC KTS infrastructure setup.
NEC recommends that the requirements and programming are completed with as much information as possible before scheduling an activation appointment with American Telephone Company.
1.5 Limitations
The following limitations apply:
 Some private IP network ranges conflict with SIP Trunking Service providers. This can cause issues when connecting to the SIP Trunking service. Private ranges reserved for the customer’s LAN are:
192.168.0.x through 192.168.10.x
 T.38 Faxing is not supported  American Telephone Company.
 G.711 is the only CODEC supported with American Telephone Company.
 The default CODEC Frame Size of 20ms must remain in command