subject: Using A T1 Line For Voice And Data Communications [print this page] People who are talking about voice or data telecommunications, often use the term T1 line. What does this mean? It can refer to a T1 physical circuit, or to the protocols commonly used for telecommunications on such a circuit. Let's take a quick look at what T1 lines are and what they can be used for.
T1 and DS1 (Digital Signal 1) are sometimes confused. To be precise, a T1 is a a communications circuit that supports digital communications. It must support a data rate of at least 1.544 mb (megabits) per second. The physical media may be fiber optics cable, copper wire, or anything else that gets the job done. DS1 is a signaling protocol, i. E., a set of rules for communications, that is used on a T1.
It was originally developed to carry voice calls between a telephone company central office and a subscriber location such as a call center. Today T1s may be used to carry any combination of voice and data over any distance.
When a T1 line is used for voice communications, it is split into 24 channels, each of which can carry a voice call in digital form at 64000 kb (kilobits) per second. Multiplying this rate by 24 and adding a few bits for signaling and framing gives us the 1.544 mb per second capacity. It is common to reserve one channel for signaling, leaving 23 channels for voice connections. This improves performance when starting calls (setup) and terminating them (tear down).
Channel allocation between voice and data is completely flexible. A business that has a lot of voice calls may use all of the 23 or 24 channels for voice. A home user with a small number of calls may use most of the channels for data, with only 1 or 2 for voice calls. Other users may select intermediate configurations.
VOIP (voice over Internet protocol) is a new technique that is much more flexible than older schemes. VOIP transforms voice calls so they can be sent over the Internet like data. It breaks them into packets at the sending location and reconstructs the complete voice signal at the receiving location. It only uses the amount of bandwidth required, which will change from moment to moment.
Internet access has become more bandwidth hungry over time as sites use more graphics and increasingly include both audio and video. Twenty years ago, T1 speed (1.544) seemed really fast. This was partly because most home Internet access was via dial up modems that maxed out at about 56 kb per second or less. Now the home user has DSL and cable modems available as alternatives, either of which may provide more bandwidth than T1.
A T1 line provides a substantial amount of telecomm bandwidth over short or long ranges. It may be used for data, voice, or both. With VOIP, voice and data sharing becomes even more efficient and self-tuning.
