T1 Lines and Options

A simple explanation of T1 lines and types.

What is a T1 Line?

by Michael Mark
What is a T1?

A T1 line is a means of transporting voice or data traffic at a rate of 1.544 Mbps, or 1,544,000 bits per second. The reliability of a T1 line is much greater than standard telephone lines or DSL. Therefore, telephone companies give T1 lines a much greater level of service. Most T1’s come with a Service Level Agreement (SLA) that will guarantee such things as speed, uptime, and latency (the time it takes for the signal to travel from one point to the other).

For the sake of simplicity, if we were to compare the flow of data with the flow of water it would look something like this. Our refrigerators and ice makers are supplied with water using a quarter inch copper pipe. This could compare to typical dialup service. It’s only needed occasionally and in small amounts. As we need more water flow the size of our pipes increase to half inch, three quarter, or one inch. This is enough to supply anything that we might use in our homes like water for cooking, cleaning, showers and sprinklers. We need this on a regular basis, but to a limited number of outlets. In the same way DSL can provide speeds to satisfy most home and small business users. To supply the needs of a neighborhood or business complex, we need a water main. The water main running down the center of our street would compare to a T1. A water main can supply all the water needs for numerous homes at the same time without being depleted. From a business standpoint, the water main can supply the water needed for an apartment complex, a hotel or a golf course.

Digital “pipelines” are available in many different sizes that can supply virtually any company’s needs. The standard North American sizes are:

  • DS0 – 64 kilobits per second (equivalent to 1 voice grade line)
  • T1 – 1.544 megabits per second (24 DS0 lines)
  • T3 – 43.232 megabits per second (28 T1s)
  • OC3 – 155 megabits per second (100 T1s)
  • OC12 – 622 megabits per second (4 OC3s)
  • OC48 – 2.5 gigabits per seconds (4 OC12s)
  • OC192 – 9.6 gigabits per second (4 OC48s)

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A Voice T1 can handle up to 24 calls simultaneously, even more if the equipment has voice compression (a term that refers to “compressing” the standard 64 kbps bandwidth per call to as low as 8 kbps). However, there is no limit to how many telephone numbers that can point to a T1. Some companies have hundreds of numbers pointing to a single T1. These numbers are called DID’s, short for Direct Inward Dialing.

DID’s can give a business great flexibility with their communications. Phone numbers can be programmed to ring directly to a department or an individual’s desk. This can ease the workload for an overwhelmed receptionist and give customers greater accessibility to their representatives. DID’s operate on the assumption that everyone in the company will not be on the phone at the same time.

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A Channelized T1 is a T1 that is split up into 24 equal channels. Each voice grade channel (also known as a DS0; Digital Signal, level zero) can transport 64 kbps—64,000 bits per second. A Channelized T1 can plug directly into a PBX for phone service. These T1’s have no features. All the special features are provided by the PBX itself. ISP’s (Internet Service Providers) also use this type of service to connect customers using dial up modems.

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Another type of T1 is an ISDN-PRI (Integrated Services Digital Network-Primary Rate Interface). Often this is referred to simply as a PRI. An ISDN PRI T1 might be called a T1 on steroids. The difference is that a PRI uses a D channel (data channel). A PRI uses one of the 24 channels available in a T1 as the D channel. This channel carries the customer call information and control signals rather than an actual call. What this means to you, the customer, is a PRI can provide the information for Caller ID and screen pops, customer information and history that “pops up” on a compute screen prior to an incoming call being answered.

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A Data T1 is exactly what the name implies, a T1 configured to transport data signals rather than voice traffic. Often synonymous with the term Internet T1, a data T1 uses the full 1.544 Mbps for internet traffic. Data T1’s have becoming increasingly more popular with the increased demand for VoIP (Voice over Internet Protocol) services. VoIP requires a reliable and stable internet connection to work properly.

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T1’s can also be used as Private Lines. A private line is a dedicated circuit between two or more locations. The terms point-to-point and point-to-multipoint are used to describe this service. Private lines are used for direct and secure access between locations. It is a way to connect PBX’s or multiple servers. Private lines can also be used to restrict internet access to a single location. When all locations are “tied” to the corporate server, the administrator can control, limit, and monitor all internet access to and from the remote location(s).

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A Fractional T1 is a T1 with limited access. The T1 is limited to a predetermined number of channels or bandwidth. A fractional T1 can be configured in the same format a full T1 can (channelized, PRI, data, etc.). Fractional T1’s are typically used for small businesses and small branch offices. A Fractional T1 will normally carry the same reliability and guarantees as a full T1.

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An Integrated T1 combines both voice and data services on the same T1. Integrated T1 service can be configured by allocating a certain number of channels to voice service and leaving the rest of the bandwidth to data or internet service. When configured in this fashion, the bandwidth for the Internet never changes. The voice channels simply lay dormant when now phone calls are being made or received.

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Another type of Integrated T1 is a Dynamic T1. A dynamic T1 is an integrated T1 that will instantly allocate bandwidth to a phone call on an as needed basis. When a call comes in or when an outside line is accessed, a device referred to as a CSU/DSU pulls the required bandwidth needed for the call and dedicates it to that conversation. As soon as the call is completed the bandwidth is released and again made available for data use.

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A Bonded T1 can give speeds over 1.544 Mbps. Bonded T1’s combine multiple T1’s to make them work as a single circuit.

So, what makes one T 1 different from another? It’s the equipment at each end. The equipment and its configuration will determine the speed, routing, type, cost, etc. of the T1. The T1 provider will also make a difference. Each T1 provider will vary in their services offered, provisioning, service guarantees, footprint, etc. T1 prices also vary greatly.

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Do we need a T1?

Several factors should be considered when determining your business T1 needs. Some of these factors are:

  • How many phone lines are needed? The greater the number of phone lines needed, the more sense a T1 will make.
  • What type of circuits can our phone system accept? Many phone systems are only set up to handle analog lines, also referred to as POTS (Plain Old Telephone Service). If your company chooses to move to T1 service, it may require upgrading or replacing the phone system.
  • Is Caller ID necessary? Are Screen pops necessary? Answering these questions will determine the type of T1 needed for telephone service.
  • Is the Internet mission critical to your business? Many companies require the Internet for orders, customer service, or direct access to vendors. If your company cannot survive a day without Internet access, a T1 should be considered.
  • Do we use software that requires the Internet? Some businesses use software that requires reliable access to the Internet. Some software companies require private lines to their server as a provision of their service.
  • How does our business use the Internet? If your business sends large files such as product brochures or graphics then a T1 is justified. Things like hosting your own website or a large number of computer users would also be contributing factors.
  • What other types of services are available in the area? Often companies have leased offices only to find that DSL is not available in their area. Many of these companies have found an integrated T1 to be the solution. Since a T1 circuit is not distance sensitive, a business beyond the reach of DSL will find the integrated T1 service a viable option.

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How much does a T1 cost?
T1’s are a bit more than DSL. Monthly rates can range from under $400.00 to over $1,500.00 depending on the T1 carrier. However, the investment can be well worth the cost. A T1 can provide a fast and stable connection for the whole company. The ROI for the additional bandwidth usually is justified by the increased productivity of those using the service. In some cases moving to a T1 can actually save the business money. Many businesses simply add new lines to keep up with their growth. One by one, their lines increase until they find themselves with 10, 15, 20 lines or more. During this time they may also purchase a new phone system that has many more features and capabilities than the simple desk phone they started with. There comes a point of diminishing return. A T1 circuit can consolidate their current services.

Carriers Choice, Inc. is an independent telecommunications agency representing dozens of T1 carriers nationwide. We take a consultative approach with our customers. Our goal is to find the perfect combination of service, price, and quality to meet our clients’ needs. Let us help you sort through all the carriers to find the perfect match for your company.

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