FWIW, T1 line repeaters were powered by up to +/- 130V DC at a constant current of 60 mA (57-63). Each line repeater dropped 8 V and could pass the rest on down the line, or loop it back if it was the last repeater.
Power was via center taps on the xmt and rcv transformers. With +130V on one and -130V on the other, the differential voltage was 260V. For shorter lines they could use other combinations of 48 and 130 VDC. Those were voltages commonly used in telephone offices for voice service (130V was used for coin collect and return on pay phones). There were specs to limit the hazard to any phone guys working on crossconnects while standing in a puddle, but it's been 40 years and I don't remember the specifics. Maybe similar to a ground fault interrupter, because it seems like 60 mA could be dangerous if the path is through your heart. In your case with a strand mounted OLT, an additional hazard would be getting shocked and then falling off the ladder or lift. From: AF <af-boun...@af.afmug.com> On Behalf Of Adam Moffett Sent: Monday, December 23, 2024 2:01 PM To: af@af.afmug.com Subject: Re: [AFMUG] RFT-V 190V Line Power distance I built a spreadsheet based on the formulas in this EETimes article I ran across: https://www.eetimes.com/line-powering-in-the-remote-dslam-world/ Initial results are that 100W at 3000m is possible, with 4x 24ga pairs or 2x 22ga pairs. One thing in that article that made me do a double take was this: How would the above be done? Sounds awesome, but I can't wrap my head around it. Two pairs to two inputs on the device? One pair between the ungrounded terminals on a +190V and -190V power supply? The effective doubling of voltage would let you run that 100W at 3000m with one 24ga pair. -Adam _____ From: AF <af-boun...@af.afmug.com <mailto:af-boun...@af.afmug.com> > on behalf of ch...@go-mtc.com <mailto:ch...@go-mtc.com> <ch...@go-mtc.com <mailto:ch...@go-mtc.com> > Sent: Monday, December 23, 2024 1:46 PM To: af@af.afmug.com <mailto:af@af.afmug.com> <af@af.afmug.com <mailto:af@af.afmug.com> > Subject: Re: [AFMUG] RFT-V 190V Line Power distance Twisted pair with pvc insulation is good for 300 volts. From: Bill Prince Sent: Monday, December 23, 2024 1:40 PM To: af@af.afmug.com <mailto:af@af.afmug.com> Subject: Re: [AFMUG] RFT-V 190V Line Power distance There has to be some metric other than just watts. 190 volts at ~~ 1/2 amp gets you your 100 watts, but so does 190 amps at a 1/2 volt. More volts means you can use smaller diameter wire, but more volts means you need more insulation. bp <part15sbs{at}gmail{dot}com> On 12/23/2024 10:20 AM, Adam Moffett wrote: I'm looking at strand mounted OLT's. One of the powering options is RFT-V which is a nominal 190VDC over twisted pair. I have 0% familiarity with it. I found a white paper from Commscope saying that the max is 100W, and at 3000 meters your 100W becomes 60W effective power due to voltage drop. Is that a fair rule of thumb? Hey Chuck, didn't you have an excel calculator for this? _____ -- AF mailing list AF@af.afmug.com <mailto:AF@af.afmug.com> http://af.afmug.com/mailman/listinfo/af_af.afmug.com
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