# T1 Lines and DS0's

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Ok, so I'm watching CBT Nuggets and Jeremy's talking about T1 lines and DS0's, explaining the channels, TDM, and CAS/CCS.

I'm trying to figure out how the physical characteristics of the line translate into the logical characteristics, but I can't find any good pictures or info about the physical characteristics/makeup of a T1 line. Does anyone have any good links or a good explanation?

I understand for ethernet cables, or regular CAT5, we have 8 stp of wires, so I'm trying to understand how the T1 cable works.

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A T-1 uses two copper pairs, one for transmit and one for receive.
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Thanks!

A few more questions...

1.) So a single T1 line (1 pair of wires for send, 1 for receive) has 24 digital channels?

2.) And a T1 trunk line, which I'm reading is 25 pairs of T1 cables, is just a bunch of separate T1 lines chunked together for what purpose?

3.) Also, I'm seeing T1 lines referred to as DS1 and DS0 in separate writeups/explanations. A T1 can use either signalling rate? Or is it that a DS1 is a signalling rate allowing for the 24 DS0's on a single cable? (I'm lost on this one.)
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1. Yes, 24 channels or time slots.

2. The T-1 trunk would just serve as aggregation for a bunch of T-1s. Kind of like a 25 pair cable terminating on a 66 block for multiple phones.

3. A DS0 is a single channel and 24 DS0 = 1 DS1.
An expert is a man who has made all the mistakes which can be made.
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Very cool. Thank you, Networker.
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darkerosxx wrote: »
Thanks!

A few more questions...

1.) So a single T1 line (1 pair of wires for send, 1 for receive) has 24 digital channels? Yes each channel is 64k. With another 8k for over head.

2.) And a T1 trunk line, which I'm reading is 25 pairs of T1 cables, is just a bunch of separate T1 lines chunked together for what purpose?

You will never see this part as it is on the telco's cable plant.

3.) Also, I'm seeing T1 lines referred to as DS1 and DS0 in separate writeups/explanations. A T1 can use either signalling rate? Or is it that a DS1 is a signalling rate allowing for the 24 DS0's on a single cable? (I'm lost on this one.)

A DS1 is a digital t-1 a dso is a 56k frame relay circuit used for monitoring in a lot of instances for remote equipment. Such as a control alarm on a remote piece of equipment.