T1 Dedicated Line FAQ's
What Is T1, DS1 Service? How does T1, DS1 work?
T1 or DS1
type of telephone service capable of transporting the equivalent of 24 conventional telephone lines, using only two
pairs of wires. T1 or DS1 uses two pairs of copper wires (four individual wires) to carry up to 24 simultaneous
conversations ("channels"), that would normally need one pair of wires each. Each 64Kbit/second channel can be
configured to carry voice or data traffic. Most telephone companies allow customers to buy just some of these
individual channels, a service called fractional T1 or DS1. Typically, fractional T1 or DS1 lines are sold in
increments of 56 Kbps (the extra 8 Kbps per channel is used for administration purposes). One of the most common
uses of a T1 lines or DS1 connections is an " Internet T1". This connection is used to provide Internet access to
businesses of all sizes. Available in over 95% of the lower forty-eight states, Internet T1s have become one of the
most popular ways for multiple users in one location to connect to the Internet. The connection is available from
dozens of providers with monthly prices for Internet T1 service ranging from $300 - $1,500. The longer the T1 or DS1
circuit, the more you pay. Installation will vary depending on the company providing the T1 or DS1 , the type of T1
or DS1, and the length of the contract for service, in some cases installation may be free.
How Can One Data Circuit Turn Into 24 Telephone Lines?
lines into one and back into 24 again is a fascinating aspect of T1 or DS1. Here's how it works: At one end of the
T1 or DS1(the central office, for example), each of the 24 phone lines is encoded to a digital format, much like a
CD recording. Then, the packets of data from each line are transmitted in sequence into a single data stream. The
device that makes this process possible is called a "channel bank," which is a small
digital telephone system with an input for T1 or DS1 and 24 outputs, one for each telephone line. At the other end
of the T1 or DS1 (the TAS, for example), another channel bank reverses the process by separating the data stream
into the original 24 distinct data packets representing each phone line. The data is then decoded from digits back
into the 24 telephone (voice) lines.
How much does an Internet T1 or DS1 cost?
The price of an Internet T1 or DS1 is generally made up of two components: the local loop price and the
port price. The local loop is what connects your location to the carrier's POP (Point of Presence). Local T1 or DS1
loops are priced according to the distance from your location to the carrier's POP and are priced differently by all
carriers. If you are looking for T1 or DS1 prices it is best that you receive quotes from multiple carriers to
insure that you get the best deal available. As a rule you can expect an Internet T1 or DS1, including local loop,
to cost between $400 and $1,300 a month, depending on the installation location and the desired speed of the
Do all carriers provide the same type of T1 or DS1 service?
Just because a carrier says that they are providing a T1 or DS1 to the Internet; do not assume that all
carriers are providing the same service. Every carrier uses different technology and design in transmitting data
from your location to the Internet. Large carriers like AT T, Qwest, Sprint and WorldCom use fiber optic backbones
that they own and operate. These networks are highly sophisticated and redundant and can move data at speeds up to
OC-192. When you buy access from one of these providers - or from a rebiller of their T1 or DS1 service - you are
getting the highest quality available. Some smaller providers will buy access from a large Tier One provider then
resell the service to a large number of subscribers, resulting in
poor quality. If you have questions about what network a T1 provider is using, we would be happy to provide you with
the answers that you need.
What's the difference between DSL and a DS1 or T1 line?
The primary difference between DSL and a DS1 or T1 is in the level of over subscription that occurs before
the service reaches the end user. When you purchase a full DS1 or T1 of Internet access, what you are generally
getting is access to 1.544 Mbps of transmission on the carrier's network, regardless of what other customers are
transmitting and receiving. To better illustrate this, let's assume that a carrier has capacity for 150 Mbps at any
given time. This means that the at the most, they would sell is 100 T1s; Tier One carrier networks are seldom
oversubscribed. For every megabyte of capacity, they can sell one megabyte access to a customer. DSL works
differently - and costs less - because of over subscription. When you use a DSL connection your service runs through
a piece of equipment called a DSLAM, as opposed to running directly into the Internet. The DSLAM acts as a point of
aggregation between the DSL subscribers and the direct connection to the Internet (normally a T1 DS1 or DS3).
Typical DSL over subscription rates run from 4:1 to 25:1. Or in other words, for every one megabyte of demand coming
into the DSLAM, a fraction of that is available. The benefit to this design is that a DSL provider can provide a 2
Mbps connection for a fraction of the T1 or DS1 price. The disadvantage is that when the DSLAM gets busy, your
connection speed will slow considerably.
Who Uses T1, DS1 and Dedicated Lines?
The telephone companies have used DS1 or T1 for decades to economize on cable runs between central offices.
In the last 10 years, T1 or DS1 has become commercially available for high-volume telephone service
What Is a T1 or DS1 Circuit?
T1 or DS1 is a high-speed data circuit with four wires, two of which are used for transmitting and
the other two for receiving. The T1 or DS1 is capable of transmitting and receiving data at a rate of about 1.5
million bits-per-second (BPS). Thus, the T1's data transmission rate is more than 100 times faster than a PC modem
operating at 14,400 BPS.
Can T1 or DS1 Be Used for Both Telephone (Voice) and Data
With a piece of equipment called a multiplexer (which is similar to a
channel bank), the T1 or DS1 can be distributed into data circuits and voice channels. For example, a T1 or DS1
could be used to carry 12 telephone lines plus two data circuits at 386K baud.
What Are the Main Advantages of T1 or
DS1 to the TAS?
The main advantage of T1 or DS1 is cost savings over equivalent
regular analog lines. Another advantage is that T1 or DS1 is a digital transmission and therefore less prone than
regular phone lines to loss and interference.
What Are the Main Disadvantages of
T1 or DS1?
The main disadvantage of T1 or DS1 is that it requires a channel bank, a
multiplexer or a digital switch to convert the signal to telephone lines. While T1 or DS1 is very reliable, another
disadvantage is that an outage could take out all 24 lines at once.
What Are the Main
Applications of T1 and DS1 in the TAS Industry?
1. Replacement of local DID trunks. Your local
trunks can easily be replaced by T1 or DS1 service from your local telephone company. In most areas, a 24-line T1 or
DS1 costs about the same as 12 DID trunks. (Costs can vary greatly for both DID trunks and DS1s or T1s, so check
with your local telephone company first.) All of your existing DID numbers can be moved to the DS1 or T1, where they
are called DNIS (pronounced "dee-niss") digits (Dialed Number Identification Service).
2. Long-distance carrier
dedicated service. T1 or DS1 service can be purchased from New Edge Networks, Covad, Verizon, AT T, MCI, Sprint or
other long-distance carriers as a dedicated connection for taking 800/888 calls and making outbound long-distance
calls. The main advantage of this service is that the long-distance company provides highly discounted rates on T1
or DS1 dedicated service. The decision to use this service should be based on your projected savings versus your
monthly T1 DS1 charges plus equipment costs. If your long-distance usage is more than 20,000 minutes per month, it
is probably worth investigating a long-distance
T1 or DS1 connection. Unfortunately, long-distance T1 or DS1 service cannot be used to carry local DID. Also, the
long distance T1 or DS1 can only handle traffic from the specific carrier (e.g., MCI) that provides the T1 or
3. Point-to-point connection between offices. T1 or DS1 can also be used to connect the lines between two
locations. For example, a T1 or DS1 circuit can be used to provide 24 off-premise extensions of lines that ring at a
remote location. Because T1 or DS1 is only one circuit, the mileage fees are significantly less than those for 24
individual lines. T1 or DS1 solutions such as this allow an operation to close down a remote TAS office by
transporting the lines to an alternate location. Depending on where the terminating locations are, this type of T1
or DS1 service may be provided by the local telephone company, a long-distance company or an alternate
Can T1 or DS1 Be Used to Link Two Office Networks Together?
Since T1 or DS1 is capable of transporting data about 100 times faster than most PC modems, it can be used
to create a wide area network between two offices. Keep in mind, however, that T1 is only one-sixth as fast as
standard office computer networks.
What Equipment Do I Need for T1 or DS1 Telephone Service?
If you have a digital switch or TAS equipment with digital capability, you only need to
purchase a T1 or DS1 card for your system. T1 and DS1 cards usually have a 24-line capacity and can be directly
connected to the T1 or DS1 circuit. However, if you do not have digital telephone equipment, you will need to rent
or purchase a channel bank whose trunk cards are compatible with the type of lines being used. For example, if all
the lines were coming in as DID, the cards must be DID compatible. As a rule, channel banks are incredibly sturdy
pieces of equipment with virtually a zero failure rate. There are no moving parts to
break, no keyboard controls to mistype on, and no disk drives that may fail. If the channel bank has a critical role
in your operation, at least one spare also should be acquired. New channel banks cost between $4,000 and $7,500;
in your operation, at least one spare also should be acquired. New channel banks cost between $4,000 and $7,500;
used banks are about half that price.
What's a CSU?
service unit or CSU is sometimes required by the telephone company. The CSU is a protective device similar to a
modem that is wired between the T1 or DS1 connection and the channel bank. The CSU typically has diagnostic and
status lights to help identify problems with the T1 or DS1 circuit. A CSU can be purchased new for around
Do I Really Need To Buy All Of That Equipment?
If purchasing and
maintaining T1 or DS1 equipment is an intimidating thought, consider renting from the long-distance carrier or the
telephone company. They will provide, install and maintain both CSU and channel banks at your location, delivering
the 24 lines to you. The cost of renting equipment is usually a few hundred dollars per month as opposed to the
thousands required to purchase the same equipment.
T1, DS1 or Not T1, DS1? how do you know what
T1 or DS1 is a reliable, manageable technology that offers the possibility of
services and reduced costs. The final decision should depend on your company's specific needs and economic
situation. Consult one of DSL-Experts T1, DS1 professionals if you still have questions regarding T1 and DS1