Integrated access device

The term dates from the era when a business bought voice and data as one bundled T1. It has outlived that circuit because the architecture keeps being right: one box, one WAN bill, and one management plane for both services.

IAD vs. ATA: what’s the difference?

An analog telephone adapter converts between analog telephony and packets — FXS ports on one side, IP on the other. That conversion is one component of an IAD, not the whole device. The IAD adds two things a standalone ATA does not have: IP routing for the site’s data devices, and termination of the WAN link itself. Put simply, an ATA plugs into someone else’s router; an IAD is the router.

IAD vs. voice gateway

A voice gateway translates between telephony domains — SIP trunks to analog lines, PRI to IP — usually as one element inside a larger network, and it typically does not route the site’s general data traffic. An IAD faces the premises instead: it delivers the site’s voice and data over one access link. The categories overlap in practice, so the useful test is functional: does one appliance terminate your WAN, route your LAN, and present your analog ports? If yes, it is doing an IAD’s job, whatever the datasheet calls it.

IAD vs. cellular router

A data-only cellular router terminates a cellular WAN and routes Ethernet or Wi-Fi — and nothing else. It has no FXS ports, no dial tone, no ring voltage, and no way to serve a fax machine or an alarm panel. A cellular gateway with true FXS telephony closes that gap; when it also routes the site’s data, it is a cellular IAD. For a site with analog devices, that distinction is the whole decision.

Traditional T1/DSL IADs vs. modern LTE/5G IADs

	T1/DSL era IAD	Modern cellular IAD
WAN access	T1/E1 or DSL circuit	LTE or 5G, often dual-SIM
Voice transport	Channelized TDM or early VoIP	VoIP engineered to preserve analog behaviors — DTMF, ring-down, alarm formats — in supported configurations
Power resilience	Little or none on the IAD itself	Integrated battery backup, commonly up to 24-48 hours depending on model and load
Management	On-site configuration, per-unit	Remote fleet provisioning and line-status monitoring
Failure mode	Died with its circuit	The cellular path is itself the continuity plan

The access technology changed; the consolidation logic did not. What changed most is resilience: a T1 IAD went down with its circuit, while a cellular IAD with battery backup is deployed precisely to survive circuit and power failures.

How does an IAD support POTS replacement?

POTS line replacement succeeds or fails on the analog side: the appliance must present RJ-11/FXS ports with the dial tone, loop current, DTMF, and disconnect behavior legacy devices expect. A cellular IAD provides that while carrying the calls over LTE or 5G — and because the same appliance routes data, it can simultaneously serve as the site’s fixed wireless access connection or its internet backup path. One installation replaces the copper voice lines and hardens the site’s connectivity in the same visit.

Which POTS IN A BOX® products are IADs?

The qualifying test is voice access plus customer data routing in one appliance:

• 90X5 — the fullest expression of the architecture: a modular gateway with Gigabit Ethernet routing, 4-8 FXS voice lines, and 5G RedCap WWAN with LTE fallback, in independently swappable modules.
• 90X1 and 90X2 — 8 FXS ports, Ethernet WAN/LAN, an optional wired NAT router with SD-WAN, and 5G or LTE cellular WAN with internet failover: modern cellular IADs optimized for POTS replacement.

The CDS-9090 and CDS-9010 also pair FXS voice with Ethernet and Wi-Fi routing for larger-site and compact deployments, and the VAB-1 includes an integral router alongside its 8 plug-and-play lines. Capabilities vary by model — the product pages list each device’s interfaces and routing options.