WOW!!! Loooong loop!
Should they set all the repeaters on thru or loop at a certain point? Yes. “Where†the span needs to be set to “loops†depends completely on the actual resistance of the copper span being used.
TOTAL EFFECTIVE SPAN RESISTANCE = cable resistance (ohms) + (180 ohms times number of repeaters in line) + simplex resistance of the terminating device (ohms) + 585 ohms
(the 585 at the end of the formula accounts for, Open Power Loop Detection and Restore option on the intelligent units.)* When using the above formula to calculate where to loop the power, omit “simplex resistance of the terminating device (ohms)†but for the loop in the entirety you’ll have to add the 585 ohms for open loop detection twice.
Also once the 7239 (ILR) is set to “loop†the end-section of the span needs to be back-fed power from the customer/end-user loop-back device.
For example, if you have the 13th repeater set to “loop.†Repeaters 1-12 would be set to “through and normal power.†Number 13 would be set to “loop†and repeaters 14-19 would be set to “though and back-power.†Power provided for repeaters 14 through 19 would come from the T1 NIU (network interface unit) and the end-user.
