1. Update the latest software version.
2. Login in to Admin mode and click the Advanced Tab.
3. Configure the T1 with Single SIP account, as shown in figure. According the SIP settings by SIP provider, Set the call Capacity (This is important for Call quality and simultaneous calls)
4. Follow the above steps for configuring other trunks T2 to T4, with respect to your SIP accounts provided by SIP provider.
Note: SIP Account should be unique for T1 to T4.
5. Configure the L1 in Voice Settings Tab, As shown in the below Figure,
6. Follow the above steps for configuring other Lines L2 to L8. If you have two sip accounts, configure the Lines by selecting T1 for L1 to L4 and T2 for L5 to L8. According to the availability of sip account configure the Trunk and Link.