A T1 line consists of one or two twisted pair of copper telco wiring that runs between your business location and the telephone company central office (CO) where your line terminates. The incumbent local telephone company owns that run of copper, but that doesn’t mean that you have to buy your T1 service through the phone company. In fact, you’ll probably get a better deal from one of the many competitive T1 service providers who offer these lines.How can that be? The phone company owns the copper, but they lease out unused pairs at attractive rates. It’s all part of the telecom deregulation process that’s taken place in recent decades. Competitive service providers who are capable of supplying T1 service then vie for your business and will lease the copper connections necessary to connect to your facility.
Note that I said T1 can be provisioned over one or two twisted copper pair. The original specification for this line service required two copper pair. One is used for transmit or upload. The other is for receive or download. There is a specified voltage, wave shape and pulse width defined for the line signals. The transmission rate is 1.5 Mbps over 6,000 ft. runs before the signal degrades too far to be usable. To go farther, electronic boxes called signal regenerators are placed at 6,000 ft. increments to restore the T1 signals to their original characteristics. Based on this technology, T1 lines can reach many miles into the countryside to connect just about any business location.
You may find that your T1 line comes in on just one pair of copper wires. That’s due to a newer modulation technology called HSDL2 that can transport both transmit and receive signals over the same wire pair up to about 12,000 ft. That’s sufficient to reach most business locations.
Your T1 service will be provided to you through an interface connection called a “smart jack.” This small electronics box connects to the incoming copper wire and gives you a port over an RJ-48C connector. This jack looks like a standard Ethernet RJ-45, but uses a keyed connector. You need a specialized cable that plugs into the RJ-48C and connects to your equipment on the other end. Your equipment will need a “T1” interface card or “ISDN PRI” interface card if you are using ISDN PRI telephone service. The T1 signal is unique and not directly compatible with Ethernet or other digital signals.
So much for the physical attributes of T1. Now let’s look at how T1 bit are organized. When used for telephone service, T1 lines are organized at 24 channels or time slots of 64 Kbps each. One channel can support one telephone call. When used for data transmission, the channel divisions are ignored in favor of a single 1.5 Mbps “pipe.” This pipe is symmetrical. You have the same 1.5 Mbps in both upload and download directions.
What about ISDN PRI? This is a special format of T1 telephone service that consists of 23 channels that can provide 23 separate business telephone lines. The 24th channel is used for switching signals and Caller ID / ANI information.
A further attribute of T1 lines is that they can be bonded together to create higher bandwidth lines. If 1.5 Mbps isn’t enough, you can get double bonded or 2xT1 service that combines 2 T1 lines for 3 Mbps. Yes, you can keep adding lines until you reach a practical limit at about 10 or 12 Mbps.
How about your business? Could you benefit from T1 line service or a better price on the T1 service your have now? If so, there are excellent deals available on T1 and bonded T1 line service right now. Get competitive quotes and see for yourself that T1 is more affordable now than ever before.
