T1 line definition
T1 line refers to a type of fiber optic telephone line that can handle more data than traditional telephone lines. It offers a transmission rate of 1.544 Mbps, which is significantly higher than standard telephone lines. T1 lines are often used by small to medium-sized businesses, private networks, voice services, and remote access.
Compared to fiber optics, T1 line is more widely available and is easier to install. However, T1 is also significantly slower.
See also: Time division duplex, DSLAM
How does T1 line work?
A T1 line consists of 24 individual channels or Digital Signal 0 (DS0) channels. Each of them can carry 64 kilobits per second (Kbps) of data. Data is transmitted in frames. Each frame is 193 bits long, or 24 channels × 8 bits + 1 framing bit. The framing bit helps to synchronize the receiver with the incoming data stream.
The T1 line uses Time Division Multiplexing (TDM) to combine the 24 channels into a single transmission path. This technology often relies on a line coding method called Bipolar with 8-Zero Substitution (B8ZS) to maintain synchronization and error detection. It replaces eight consecutive zeros in the data stream with a special pattern to ensure there are enough transitions to maintain the receiver’s clock synchronization.
