http://blogs.technet.com/jkunert/archive/2008/10/31/migrating-large-tdm-pbx-systems-to-voip-solutions.aspxThis article describes aspects of the migration process from a TDM (Time Division Multiplexing) PBX to a VoIP solution like Office Communications Server. TDM to VoIP migration using PRI tie lines A large enterprise TDM PBX consists of one or multipleen-USCommunityServer 2.1 SP1 (Build: 61025.2)http://blogs.technet.com/jkunert/archive/2008/10/31/migrating-large-tdm-pbx-systems-to-voip-solutions.aspx#3150360Mon, 10 Nov 2008 13:03:43 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3150360wout<p>Nice article and a good overview of migration paths!</p> <p>One small comment though, there is HW needed to communicate from VoIP to TDM; DSP ports. Depending on the amount of traditional TDM user on the IP PBX there could be a growth of VoIP traffic, thus using more TDM ports. </p> http://blogs.technet.com/jkunert/archive/2008/10/31/migrating-large-tdm-pbx-systems-to-voip-solutions.aspx#3152933Fri, 14 Nov 2008 11:11:47 GMTd5e57398-b9ef-4490-9955-07cbb4e4a80d:3152933zarst<p>Doing this in Europe using E1 instead of T1, the need is approx. 6 E1 GW interfaces instead of 8 GW interfaces. (8*23=184 channels, 6*30=180 channels)</p> <p>Since every interface HW (Both PBX and GW) costs about 5000 $ the saving is approx 4 *5000 $ (2 PBX interfaces, 2 GW interfaces).</p> <p>/Torbjorn </p>