Yes, Wave was built for SIP – both SIP Trunks and SIP (IP) phones.  While some other phone systems claim to use “SIP”, they may be using a proprietary implementation of SIP which requires you use special phones specific to their systems.  Vertical Wave does not use proprietary SIP.  While there are several “certified” IP phones for use with Wave, any non-proprietary SIP device (phones, gateways, door controls, paging systems, etc) will work with Wave.  SIP Trunk functionality is built into Wave and enabled with a “SIP Trunk Services” license.  While SIP has recently become a popular way to do trunking and phones nowadays, Wave does also support T1/PRI, E1/BRI, and analog trunking, as well as both analog and digital stations.  Many customers who migrated to Wave from their legacy PBX have kept their previous analog or digital phones in place.