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New Member

Cable length long vs short



I am trying to understand the difference between cable length 0db and cable length short and how to use them correctly. I don't know what the lengths are that define long vs short. Ex. If I have a router racked up and using T1/E1 card for a T1 circuit. I'm using a 4 foot cable between the card on the router to the providers card. This card is extended from the DMARC which is in the basement maybe 100 feet. Is this command long vs short based on  the cable between the router and vendor card or is it between the router and the DMARC? I would think it would be the vendor's card. My next question is do most people always use long? That's what one of my co-workers told me. In the above ex. my setup is exactly like this and currently it's set to "cablelength is long 0db" Could one end of the T1 have long and the other short without causing any issues? I would think it wouldn't matter but figured I would ask. 




T1 only. cablelength long

T1 only. cablelength long attenuates the pulse from the transmitter using pulse equalization and line build-out. This command applies to cables longer than 660 feet. Loss values are:





Default attenuation is 0db.

cablelength short sets transmission attenuation for cable lengths of 660 feet or less. Cable lengths can be specified as follows:

110 for cable lengths from 0 to 110 feet

220 for cable lengths from 110 to 220 feet

330 for cable lengths from 220 to 330 feet

440 for cable lengths from 330 to 440 feet

550 for cable lengths from 440 to 550 feet

660 for cable lengths from 550 to 660 feet

There is no default cable length.

New Member

Thanks for the reply. I came

Thanks for the reply. I came across the following post on Cisco from awhile ago as I'm having issues with a pt. to pt. T1. When it comes to clocking should you setup both ends of the T1 to be "clock source line" or do you want one to be line and the other end internal? 


Use Line for clock source.

Use Line for clock source. let the telco DACS do the circuit timing.

There are only a few cases where the router should provide the line timing.