Start here
If you've just received a retirement notice
These three, in order. Together they cover what the notice means, what's on your lines, and how to plan the replacement.
[ 01 · regulatory ]
Copper retirement & the PSTN sunset
What the FCC's March 2026 Network and Services Modernization Order changed, what notice you're entitled to, and how the carrier timelines actually run.
Read →[ 02 · migration ]
POTS line replacement
Finding every analog line, classifying it by criticality, and choosing between cellular, SIP ATA, and native IP replacement per class.
Read →[ 03 · migration ]
TDM to IP migration
Trunk sizing, feature parity, cutover sequencing, and the differences between a PRI and a SIP trunk that bite during cutover.
Read →Legacy telephony
The infrastructure being switched off. Written for people who have to work on it, not for nostalgia.
[ analog ]
PSTN & POTS fundamentals
Loop start versus ground start, the local loop, central office batteries, and why analog lines survived this long.
Read →[ tdm ]
T1, DS1 & fractional T1
1.544 Mbps, 24 DS0 channels, the 8 kbps of framing, D4 versus ESF, AMI versus B8ZS, and how fractional service is provisioned.
Read →[ signaling ]
ISDN PRI & BRI
23B+D, the D-channel, NFAS, and the feature behaviors that have to be reproduced when a PRI becomes a SIP trunk.
Read →[ signaling ]
SS7 & call signaling
Out-of-band signaling, ISUP call setup, SS7 network elements, and how the same work is done in a SIP world.
Read →Migration & IP voice
Getting from there to here without stranding anything.
[ regulatory ]
Copper retirement & the PSTN sunset
The March 2026 FCC order, Section 214 discontinuance, notice requirements, and 911 coordination obligations.
Read →[ migration ]
POTS line replacement
Inventory, classification, and replacement paths for elevator phones, fire panels, door entry, fax and card terminals.
Read →[ migration ]
TDM to IP migration
Traffic studies, Erlang B trunk sizing, feature parity matrices, and cutover sequencing.
Read →[ ip voice ]
SIP trunking & session border controllers
What an SBC does as a B2BUA, topology hiding, SIP normalization, call admission control, and media handling.
Read →Contact center & AI
Where the traffic ends up, and what's answering it.
[ ccaas ]
CCaaS migration
Selection criteria that discriminate, integration inventory, historical data strategy, and phased cutover.
Read →[ measurement ]
Voice quality: MOS, R-factor & POLQA
The ITU-T G.107 E-model, what an R-factor actually is, POLQA (P.863) versus PESQ, and the budget for latency, jitter and loss.
Read →[ ai ]
Evaluating an AI agent for production
Why containment, deflection and resolution are three numbers, building an evaluation set, and defining go-live criteria.
Read →Compliance
Three regimes that attach to an ordinary contact center, usually owned by three teams who each assume another has it.
[ 911 ]
E911, Kari's Law & RAY BAUM'S Act
Direct dialing, on-site notification, dispatchable location, and how the obligation differs for fixed, nomadic and off-premises devices.
Read →[ caller id ]
STIR/SHAKEN & robocall mitigation
Attestation levels, the Robocall Mitigation Database, annual recertification, and what happens to your calls if you're not listed.
Read →[ payments ]
PCI DSS in the contact center
Why pause-and-resume no longer holds up, DTMF masking, scope reduction, and where cardholder data actually flows.
Read →[ reference ]
Glossary
Ninety-plus terms across analog, TDM, signaling, IP voice, contact center and AI — defined in one place.
Read →