T1 Line

T1 Line : Origin & Dynamics

Bell Labs proudly devised a T-carrier signaling scheme called Digital signal 1 (DS1) or also called as T1. This type of line has been widely used in North America and Japan for transmitting voice and data between devices. For those outside in these countries, E1 is used.

To have a clear idea of what a DS1 is. The following discusses its features:


It is made up of 24 digitized voice channels, each channel carrying 64 kilobits per second. Being a full-duplex circuit allows it to transmit and receive 1.544 megabits per second.

Frame Synchronization

This is required to determine the timeslots with each 24-channel frame. This is how it works: synchronization happens by allotting a framing which in turn makes in 8 kbit/s of framing data per DS1. Since this 8-kbit/s channel is utilized by transferring equipment overhead, only 1.536/s is actually transmitted on to the user. Framing schemes could either be Super Frame and Extended Super Frame. The first is made up of twelve consecutive 193-bit frames while the latter consists of twenty-four 193-bit frames of data. Because of this difference, these two schemes are incompatible and are used differently.


In case of DS1, there are times when the connectivity maybe lost in one direction while the other still have it. Connectivity here refers to the ability of DS1  to transmit client data from either end to the other.


When the framing weakens, alarms activates through the receiving terminal equipment. Red alarm signals the alarming equipment was not able to retrieve the framing reliably- corruption or loss of signal. Yellow means reception from the far end of a data or framing pattern that reports the far end is in “red alarm.” Lastly, blue signals a d disturbance in the communication path between the terminal equipment.

Interesting Facts

Name Origin

The name T1 gets its name from the carrier letter assigned by AT&T to the technology. Basically, the “T” is a part number that was designated by AT&T. DS-1 meant “Digital Service – Level 1″(originally 24 digitized voice channels over the T1). The terms T1 and DS1 have grown synonymous and include numerous different services from voice to data to clear-channel pipes.


If you are still in doubt, Dark fiber are used as alternatives to unused fibers,  available for use. Dark fiber can be found everywhere in replace of a DS1.


The T1/E1 protocol has a semiconductor  and its basic purpose is to recover the information from the “line”, i.e., the conductive line that transversed distance.

T1 Line : How it Works?

When we think about transmitting voice and data we often connect it to the usual telephone lines we’ve grown to recognize to be the carrier of the two ever since. But have you heard that there’s a new trend in transmitting voice and data that is a lot times better than a twisted copper telephone lines? Yes, there is and it has been around for years. It is simply called T1.

T1 is a particular kind of fiber optic lines or could also be copper that can carry 24 digitized voice channels or transmit 1.544 megabits per second. This sounds really good compared to a normal phone line that can only carry 30 kilobits per second. T1 carries 60 more times of data than a normal residential modem.  It works this way; if the T1 line gets plug into the office’s phone system then it’s ready for telephone conversations while getting it plug into the network’s router allows it to carry data.

Another key feature that makes a T1 line better again than an analog modem is its reliability. If the users are not really doing some heavy downloading at the same time, T1 line assures you that it can handle many users quite well. There would be no problem even if there are hundreds of users in one T1 line when they are simply doing general browsing.

Of course it is important as well to know how much you will be paying for a T1 line. Because of all its good features, it is also somehow costly than your traditional phone line. However, it is really more practical when a business have more than 8 telephone lines as this lessens telephone charges while providing high-speed internet access. Price of a T1 line ranges from $1,000 to $1,500 per month. This will depend on who is the provider and its destination. The other end of the T1 line requires to be connected to a web server. The fee the phone company charges and the fee the ISP charges combined is the sum of the cost.

For a large company, a T1 line might not suffice. The following are suggested:

  • DS0 – 64 kilobits per second
  • ISDN – Two DS0 lines plus signaling (16 kilobytes per second), or 128 kilobits per second
  • T1 – 1.544 megabits per second (24 DS0 lines)
  • T3 – 43.232 megabits per second (28 T1s)
  • OC3 – 155 megabits per second (84 T1s)
  • OC12 – 622 megabits per second (4 OC3s)
  • OC48 – 2.5 gigabits per seconds (4 OC12s)
  • OC192 – 9.6 gigabits per second (4 OC48s)

Price of a T1 line might back one off but the good news is prices are dropping. There are many providers who will you sure service that is really worth what you are paying for.

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