subject: T1 Lines - The Most Common High-Speed Circuit [print this page] T1 Lines - The Most Common High-Speed Circuit
T1 lines are typically sold in any of three ways: Full T1, Fractional T1 and Channelized T1. T1 circuit is a dedicated circuit and is normally made up of two parts: local loop and carrier circuit. The local loop is provided by your local telephone company since they are the ones that place the wire connected to the site in the ground. If the T1 end is for the Internet the other circuit end is routed to your selected telecommunications provider so that the Internet service will be activated. Therefore, your T1 Internet must contain the local telephone company circuit portion nearest to you, as well as the Internet provider portion of the circuit. When troubleshooting T1 always keep in mind that you need to get your local phone company and Internet provider together over the phone to work out on the circuit.
Usually, large Internet Service Providers own the local circuits and are also the local telecommunications provider but this is quite uncommon. Often when you purchase T1 line, you are buying T1 where the local telephone company's circuit portion is resold by the Internet service provider as a full T1. And this is the better way to buy because you can hold the provider responsible for all problems in the local company's part of the circuit yet this can be expensive. The T1 circuit has an always on' connection. It does not resemble a voice circuit that only produces expenses once a call is placed. Hence, T1 lines are sometimes referred as dedicated lines or private lines because they are always used, whether for data transmission or otherwise. Thus, this line can never be used to carry traffic from several subscribers. This is because T1 lines are dedicated circuits that cost more than Frame Relay or ISDN circuits that assume shared customer connection with other subscribers. Since T1 lines have an 'always on' capacity they are dedicated data lines.
The T1 circuit is the first level in the multiplexing of digital signal multiplexing system. T1s make use of a certain Stratum 3 clock in maintaining the clocking' of the line. The devices that support a T1 line estimates synchronization with T1 based on data received on the link. Therefore, T1 communication is not always completely synchronous. Some call T1 lines as pleisiosynchronous connections to define it appropriately. But T1s are better understood when referred to as DS1. A T1 speed can be as high as 1.5Mbps on the circuit. These lines are probably the most common high-speed circuit provided by telecommunication carriers since a T1 can be restored and extended in order to reach any site. Other Internet solutions such as DSL do not have the same speed total as a standard T-line service. T1s carry twenty-four channels of digital information and maintain a specific level of density for T1 to assure the clock is consistently maintained at both circuit ends.
