Grandstream is a technology partner of 3CX. Grandstream’s IP phones and GXW-410x gateways work very well with 3CX IP PBX software. The following link on Grandstream’s website shows the close relationship between these two organizations.
Title: 3CX and Grandstream Partner to Deliver Windows-Based IP-PBX Solution for the SMB Market
http://www.grandstream.com/documents/Gr ... bility.pdf