I'm working on a new government circuit that is a 4.8K DDS (pin 1,2,7,8). I have a CSU/DSU designed for this, but the demarc is in one building and the user equipment is in another building. There are potentially dry copper pairs between the buildings but I don't know the distance yet. What is the max cable distance for DDS with no repeaters?

I'm used to using ADC Pairgain modems to extend T-1 circuits. Does something exist for extending DDS?

Any assistance would be appreciated.

Without a repeater, a sub-rate ckt can not have anymore that 18kft of copper. So, depending on how the ckt was delivered to the d-mark, that would determine how far past the d-mark you can extend it. If the ckt was delivered using IDSL technology (card placed in a ncte mounting at the d-mark) you have 18kft past the card to work with. If it was delivered the traditional way, over straight copper, you will just have to try it. And remember, sub-rate is terminated as an RJ48s, your pinouts are 1&2, 7&8.

(Edited due to auto-correct. Would not have been good if left)

Note: 18,000 feet is a bench mark on copper because at that distance an analog or digital signal has been proven to be attenuated to the point where it is too distorted to be read correctly.

18,000 feet is over 3 miles. I doubt your buildings are that far apart. What you could do to help insurnace sucess is: Check both the pairs you are going to use for the demarc extension by grounding the Tips and Rings at one end and with a VOM check tip to ground and then ring to ground on both pairs. You are looking for resistance within a couple ohms of each other. Then put a Tip to Ring loop on both pairs and check loop resistance again you your looking for two pairs within a couple ohms of each other.