Way back in 1961, Bell Labs introduced the T-1. We’re talking 47 years ago. For those of you unfamiliar with the T-carrier system, prior to 1961, all telco traffic was analog signaling over copper wires. Fast forward to now and you’ll still find people ordering a half-dozen phone lines from the phone company to plug into their IVR instead of buying a T-1.
As a rule of thumb, once you need to order 8 POTS (plain-old telephone service) lines from the phone company, it’s usually just as cost-effective to buy a T-1 that can handle 24 calls. A single metered phone line from Verizon will cost you around 55 dollars per month. A single T-1 with all 24 ports activated will cost you around 450 dollars per month. And no, I didn’t make up those numbers to work out so evenly.
The immediate advantage to a T-1 is the fact that it’s a single cable from the demarc to your IVR. Instead, with POTS lines, you have to contend with 8 demarc ports with 8 wires going to 8 IVR ports in a nasty snarl of silver satin wiring. Plus all of those POTS lines are subject to noise, static, and other problems that only occur on analog lines. This makes replacing 8 POTS lines with a T1 a gimme. Same cost, less hassle.
I would, however, argue for replacing as few as 4 POTS lines with a T-1 if you’re planning on taking full advantage of your Plum Voice IVR.
First, 4 POTS lines is still four times more wiring to tangle up than a single T-1 line. You’ll still save yourself headaches.
Second, POTS lines don’t know what number was dialed (the DNIS) so you can only ever run one IVR application on any given line. So if you have 4 POTS lines you can only run 4 IVR applications. With a T-1, the IVR knows what number was dialed when a call comes in on a channel and can then fire up the right application for that particular call. You can have hundreds — even thousands — of phone numbers assigned to your T-1 and any call made to any of these numbers will be sent over a free channel on your T-1 and then directed to the appropriate application.
Third, even if you were to only have 4 applications running on your 4 POTS lines, each application only has one channel available to it. If two people try and call the same number, one gets through and the other gets a busy — just like your plain old telephone service at home. On a T-1, you have 24 channels that can be used for any of your applications. Capacity is shared because, with DNIS-based application routing, every call identifies its own destination.
Fourth, POTS lines don’t tell you when they’re dead. They just quietly stop working. Both ends of a T-1 — your carrier’s switch and your IVR — are constantly trading status information. If the carrier switch ever fails, the IVR will know immediately and you’ll be able to immediately respond to the situation before your callers discover the failure for you.
Fifth, and last, ANI (commonly referred to as caller ID) requires two rings of an POTS line before it’s available to an analog IVR. Sure, call setup time is a minor matter as most callers are willing to wait 10 extra seconds for the IVR to pick up, but wouldn’t you rather have immediate transmission of ANI data and immediate call acceptance?
So unless you’re running only one application and have a high-tolerance for messy wiring, you should go out and replace anything larger than a 4-port analog IVR with an IVR with a digital T-1 interface.
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