On Thu, Jan 13, 2022 at 02:06:39PM -0800, Michael Thomas wrote: > > For my ISP, they maintain backup power for both DSL and POTS. I > suspect that for a lot of DSL that would hold true because it's > relatively easy for them to power since they already have the > battery backup requirements for POTS. The setup they have here > is a DSLAM and SIP->POTS termination in a pedestal with fiber > backhaul. They use the old copper that used to go back to the CO > to power the pedestal.
Do you happen to know what voltage is placed across the copper pairs for this purpose? Maybe 130V like T1 span repeaters? More? I used to have three POTS lines at home from BellSouth, before the AT&T acquisition, with DSL on one of them, all supposedly served from the same Lucent SLC. One of these, the one originally used for DSL, would always go down for both voice and data when the SLC lost power-- no DC, no dialtone, no DSL, while the other two remained up. Despite several claims of a resolution, this was never properly fixed, so eventually I just had them move DSL over to one of the unaffected lines. I could never understand what failure mode would result in losing just a single POTS line like this while the carrier equipment was running from battery, while others remained in service. Speculating, perhaps only the A or B-side was backed up, and an open diode or other defect caused a single ine card to draw only from the "other" source? But, at this time (circa 2000) the remote DSLAM was definitely a separate piece of equipment, right, joined to a shared subscriber pair with passive splitters? > Mike -- Jordan.
