>Date: Thu, 13 Feb 1997 14:24:37 -0500 >From: Frank McCaughey <[email protected]>
Frank, >The 130 Vdc used on the older DS-1 lines was fed, simplex, down the >Tx and back up the Rx pair, to power the repeaters. Only the longest >loops (several km) were fed +130/-130, to make 260 Vdc pair-to-pair. >For equipment used on customer premises, there would likely be no >repeaters between the customer location and the CO, and even if >there were, they would likely be fed from the CO, not the customer >premises. >As the number of repeaters increased, the powering was fed >-48V/Ground >-48/+48 >-130/Ground, and so on. >So the case where 130 Vdc would appear on customer premises would be >extremely rare, only in a specially-engineered situation, and where >other special protective measures should be taken. Actually, the span-repeater power should _never_ appear on the customer premises, this is one of the distinctions between DSX-1 and DS-1. DSX-1 (the "cross-connect" point) is supposed to be "behind" an "office-terminating-repeater." I suppose in the current deregulated U.S. market this isn't quite the certainity it used to be, since the OTR might be built-into a piece of CPE. >In other words, the case is unusual enough that a footnote would be >more than adequate in any list of requirements, rather than tar the >entire system with the same brush. I worked for GTE for many years, and in their network, 130 VDC is commonplace -- I don't know about the rest of the world. ________________________________________________________________ John Combs, Senior Project Engineer, ITS/TestMark Laboratories Email: [email protected] URL: http://www.testmark.com
