What Constitutes 'Carrier Class’?


Last time, we deconstructed the telephony hankerings of a fictitious customer, Bob, as a way to illustrate the obstacles that could block future “do-it-yourself” installs of cable-delivered voice-over-IP (VoIP) service.

A refresher: One day, Bob decided to replace the two lines of telephone service he’d gotten from his local telephone company for the past decade with a data and voice package from his local cable company. (He already had video service.) Bob liked his phone numbers, and opted to keep them.


He made the decision to switch while rummaging through an electronics store one Saturday morning. There, he discovered the bundled voice/data offer next to a stack of devices that looked like cable modems. (In trade-speak, those devices go by “E-MTA,” or “embedded multimedia terminal adaptor.” They’re cable modems with built-in VoIP mechanisms and phone connectors.)

Bob bought the gadget and took it home, reckoning he could handle the installation himself. He even thought he could get it all going before his co-workers picked him up to go to a baseball game that afternoon.

The broadband Internet connection came up quickly and painlessly. So did the VoIP connection, for the most part — although all that traipsing around outside with a screwdriver to find the telco’s wiring box, and undo the twisted-pair lines, was a little more user-intensive than he would’ve liked.


Bob was in his garage, dusting off and putting away the screwdriver, when the police car eased into his driveway, lights flashing.

Naturally, it was at this precise moment that Bob’s coworkers arrived to pick him up for the game.

Suddenly, and with a flash of chagrin, Bob remembered his home security system.

Like many such systems, the “eyes and ears” watching over Bob’s house are a series of small plastic sensors affixed to windows and doors. Their wires unite at a metal box, which, in Bob’s case, rests on an interior wall of his hall closet. The metal box connects to the telco wiring box, on the side of the house. A speaker, mounted above the closet door, is used by the alarm company to talk with Bob, when necessary.

Yet when Bob unwound the colored wires from the posts inside the telco wiring box, he simultaneously deactivated the line seized by the alarm company to contact him during emergencies.


Past the red lights of the squad car, and the smirks of his friends, Bob listened to the policeman tell him of his error. When he’d disconnected the wires, Officer Friendly said, the alarm system did what any guardian would do when its main link disappears: It called the police, lest a burglar had cut the line.

The only constant about home security systems is this: They’re different from one to the next, in terms of how they link sensors to the remote monitoring company. Systems designed to thwart burglars almost have to vary.

From a tactical, operational perspective, there’s really no getting around it: Dealing with security systems during VoIP installations is a home wiring thing.

Already, some MSOs have home security systems on the checklist of things to ask about when customers request phone service. Forewarned is forearmed.

In practice, people with home alarm systems like Bob’s are in the minority. So far, in the limited trials and commercial launches of cable VoIP, somewhere between 8% and 10% of homes use security systems that seize a phone line during trouble.

Yet it’s worth remembering that the traditional telephone network is a century old. It’s likely that there will always be small outcroppings of customers who use a small outcropping of devices that rely on the phone wires.

Some fraction of a community, for example, probably participates in the automated meter-reading practices of some utilities — which rely upon a phone line to collect data. Others use devices they may not even know they have that communicate to other devices over the phone wires.

Symptoms will show up only when the traditional telco wires are disconnected.

Think as a consumer, for just a moment. You’ve had the same phone provider for a dozen-plus years. You switch. Suddenly, something you’ve ignored for the last dozen years stops working. Who do you blame: The thing you’ve ignored for the last dozen years or the new service provider?


It is all of these things, by the way, that roll up into that everywhere term: carrier class. At a minimum, “carrier class” means that the phone works even when the power is out, at least for some period of time. But at a checklist level, “carrier class” can include triple dozens of other features.

In Bob’s case, he corrected the security situation by futzing with his wiring, so that his alarm box connection behaved like any other phone outlet in the house. When the alarm needs access to a phone line, it goes “off-hook,” through the E-MTA. Staffers at the remote monitoring location can still establish a talk-able connection over the speaker in Bob’s hall closet.

The point is this: Cable providers who sell their phone service as “LEC replacement,” meaning that they intend to fully replace the local phone service, will probably need to deal with everything that uses that phone line.

By contrast, telephone providers who industrially describe their VoIP service as “secondary line” or “nonprimary line,” among other gibberish terms, don’t have the baggage of “carrier class.” This includes Vonage Holdings Inc. and AT&T Corp.’s new “CallVantage” offerings, which run on top of cable and DSL modems. Others are coming.

Ultimately, customer Bob was able to manage his own VoIP install. But the policeman in the driveway erased some of the satisfaction, and his friends tagged him with a new nickname: For God Sakes Don’t Do it Yourself Bob.