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3845 and 2851 CME router FXS Versus T1 for legacy PBX


I am trying to decide for various PBX campuses there are 1, 2, 4, 5, 25, 100 and 200 analog phones system. For CME 2851 to interface which option would be better T1 or the FXS port. I understand we can use 4 FXS port for 4 phones tied to a PBX system, but at what number of legacy phones ( 4 and above)  one should consider T1 over the FXS port.

We need numbering scheme for various campuses to come up with FXS and T1 ports to support legacy systems.

1 Reply 1


Need to understand your question better. You are migrating the legacy PBX with Analog phones into IP PBX (CME system), and you would like to know what are the options on CME to support more than 4 analog phones? If this is the case,

- You need to know the CME platform capacities (Every analog phones will utilize a phone user count. on 2851, the maximum number of phones supported is 100, and on 3845, it is 250)

- You will also need to have VG224 to be the interface between the CME and the analog phones when the analog phones can't attach to the CME router directly. A single VG224 can connect 24 analog phones and it will convert the FXS to SCCP to allow CME control those analog phones as Skinny IP phones.

If this is not the case, can you elaborate "numbering scheme for various campuses to come up with FXS and T1 ports to support legacy systems"? 2851 is acting as GW to interact with Legacy PBX?

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