VoIP, In-HOME Wiring, and Self-Installs

The fact that all the phones in the house ring with an incoming call probably qualifies as a thing we take for granted. But if you’ve ever wondered how it is that a voice-ready cable modem can ring all the phones in the house, this translation is for you.

Home wiring of cable-delivered voice-over-Internet protocol service is an effortless mental stumble, mostly because engineers cleared that hurdle months ago. As a result, they’re vaguely dismissive when asked about it. Not dismissive in a “dumb question” way, but more in that “easy, done, not an issue” way.

Yet, it’s also true that making all the phones in a home work from one cable-modem connection is one of three big reasons why it won’t exactly be a cakewalk for consumers to “self-install” themselves for VoIP. (The other two are local number portability and home alarm systems, which we’ll get to.)


To illustrate, consider hypothetical customer Bob, who lives in a house (as in not an apartment). Bob sees himself as daring, but not always victorious, with techno-gadgetry.

One sunny day, Bob surrenders to the magnetism of “the bundle.” He decides to swap the phone service he gets from his local telephone company with a video, data and voice package from his local cable company.

Let’s say he already has video service, and is adding the data and phone parts on top.

A few other important details about customer Bob: He wants to keep both of his existing phone numbers. Plus, his place is rigged with an alarm system that comes with a guy who occasionally talks to him over a speaker near the hall closet.

The alarm guy connects to the hall closet speaker by seizing Bob’s existing phone line when emergency strikes (or, more often, when a critical battery is low enough to flake an alarm.)

So far, this is a scenario that could happen. The next part can’t — yet.

Bob buys his VoIP-ready modem and the service at a store, and decides to do the installation himself. The cable-modem hookup goes swimmingly. Soon enough, Bob feels the smug appreciation that comes with broadband speed.

Tackling the phone part is slightly more tricky. Bob begins by dutifully connecting the included phone cord from the E-MTA (embedded multimedia terminal adapter, tech-speak for a cable modem/VoIP combo unit) to the wall jack where the phone used to plug in. Probably, he fishes around for a splitter so that the phone by the PC still works. So far, so good.

Buoyed by that success, and feeling enormously skillful, Bob goes outside. He needs to locate the place on the house where the telephone company drops off its wires. He finds it — a beige plastic box, about the size of a thick college textbook — between the downspout and the woodpile, next to the garage.

The beige box is known, in telco lingo, as a “network interface device,” or “NID.” It also goes by “network interface unit,” or “NIU.” (“NID” usually gets pronounced as a word; “NIU” gets spelled out.)

The NID is a legal point of demarcation. Everything to the “left” of it is owned by the telco. Everything to the “right” is owned by the consumer.

Somehow, Bob knows that it’s the right of the telco to forbid any alien signals or energy to backwash up its wires. Alien, in this sense, means “not theirs.”

Mostly, they do that to protect their switches from electrical energy running up the wire from people’s homes, which can cause damage.


Bob unscrews the door to the NID, and carefully disconnects the colored-wire pairs for both of his lines. (Note: The older the home, and the more cumulative owners, the more elaborate the game of identifying which wire colors go with which lines.)

The NID also completes the junction of all Bob’s phone wires, strung inside the walls of his house. The linkage can be wired in two ways. One is called “home run.” That’s where twisted pair phone wires, one for each active phone number, run individually to each phone jack in the house, like bases to home plate.

The second in-home wiring method is to connect the existing phone jacks “serially.” In a series. That’s where a pair of wires (again, one pair for each line) stretches to the first jack, and the first jack stretches a wire pair to the second jack, and so on around the house. If you’re thinking “daisy-chain,” you’re in the zone.

Either way, home run or serial, the link from the NID, through the house, to all the phones, remains intact and usable — even after Bob disconnects the telco-delivered wires, outside.


When Bob phoned in to activate his new services, and told his cable provider that he wanted to keep both of his existing phone numbers — a process widely publicized in recent months as “local number portability,” or “LNP” — he could’ve sworn he heard a tiny sigh.

At best, offering LNP as part of a cable-delivered telephone service adds a few days to the activation of the product. At worst, it turns into behind-the-scenes technocratic squabbles. Result: Add more days before activation.

And then there’s Bob’s home alarm system, with the line-seizing feature and the guy who speaks to him from the hall closet. After Bob’s do-it-yourself day, that seize-able line is now two lonely, disconnected wires, in a plastic box, next to the woodpile.

That’s an overview of what cable VoIP faces, as it marches toward mainstream.

Next time: more on how Bob deals with his alarm system situation.

Stumped by gibberish? Visit Leslie Ellis atwww.translation-please.com.