I am in the process of proposing a UC520 installation, but I may need several FXS ports. I will need about four FXS ports to support an existing external paging system, as well as a few more to support some analog fax machines. I believe the 48 user UC520 has 12 FXO and 4 FXS. Are any of the FXO ports in this model removable, so that we can replace them with FXS? Or would it be better to use ATAs to connect to the analog devices?
You can actually use a SPA8000 to connect your analog devices to the UC520. Each SPA8000 unit is considered to be a single SIP phone, even if all 8 FXS ports are configured. So if you have a SPA8000 configured with 8 ports, that counts as one phone and not 8 phones, even if you have 8 extensions configured.
The SPA8000 cannot be configured through CCA. However, here is the document that explains the integration of the SPA8000 on the UC520:
This is exactly what I was talking about. I understand the licensing problem you are talking about as well, and I am not sure what discount you would be getting going from 32->48->64 as opposed to 48->64. While I know how to perform these upgrades, I am not a sales, so I do not know what each one would cost.
But, the SPA8000 option is a very good one for what you are looking for if cost is an issue.
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