Question

What are the two types of line coding for T1 curcuits?

Answer 1

here is your answer

T1 is an AT&T term for a digital carrier facility used to transmit a DS-1 formatted digital signal at 1.554 megabits per second. T1 transmission uses a bipolar return-to-zero alternate mark inversion line coding scheme to keep the DC carrier component from saturating the line. Although some in our industry consider T1 signaling obsolete, a lot of equipment operates at the "T1 rate," and such signals are either combined for transmission via faster circuits or demultiplexed into 64-kilobit-per-second circuits for distribution to individual subscribers.

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Answer 2

With T1 you get up to 24 virtual phonelines or "channels" on a single physicalline made up of two pairs of twisted copper wires. ... T1 transmission uses a bipolar return-to-zero alternate mark inversion line coding scheme to keep the DC carrier component from saturating the line.