PSTN Migration: A 12-Step Hardware Checklist

Most copper sunsets give you 18 months of notice. That sounds long until you inventory every fax, alarm panel, and elevator phone still riding analog pairs.

Step one is a physical audit. Walk every IDF and MDF. Tag each analog drop with what it serves. Half of every migration's cost overruns come from circuits nobody knew existed.

Step two is gateway sizing. Pick FXS counts based on your audit, then add an SBC if you are crossing carrier boundaries. Don't skip the SBC — it is the only place to enforce SRTP and SIP rate limits at the edge.