 LazManPremium
join:2003-03-26
canada | reply to BTS Niagara
Re: Fairly powerful shock from touching green line If either side of the pair is dead-shorted to ground, you'll get a BAD hum on the line...
As has been said, nominal voltage in North America is -48vdc. Ring current, on a standard 1FL is between 60-110vAC at 20Hz.
As for 'ground' on the one side - you'll be seeing 0v differential to ground; that's not the same thing as being grounded...
Anyways - it's possible, espically in this humid weather, to get a shock from the voltage on the line - although it's more of an annoyance then painful. The sweating we're all doing right now increases the skins conductance, and allows the lower voltage/current to pass thru the body. Ring current, is painful! 
Laz |
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 sbrookPremium,Mod
join:2001-12-14
Ottawa
kudos:4
 ·TekSavvy Cable
·Rogers Hi-Speed
| You want the belts you get from old strowger equipment ... even though you're only switching 48V to get the ring, because of all the inductors on the line, you get very high spikes on every ring pulse. We checked it with an scope and found up to 400V spikes on every cycle, measured by a true RMS meter, the result was closer to 55V ... but that kicked! |
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LazManPremium
join:2003-03-26
canada | One tester I used to work with, thought it was funny as HELL to start making 'test calls' on cables we weren't finished with. Nothing like banging your hands off the back of wire-wrap blocks as ring-current runs through you... But he got his... One day, managed to get him out into the field on a 'complex issue' - while he had a hand-full of pair, buddy at the next cross-box fired up the megger...
The tester realized that maybe he wasn't so funny after all.
Laz |
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sbrookPremium,Mod
join:2001-12-14
Ottawa
kudos:4 | Yeah, hitting him with a megger is NOT a nice idea! |
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 joshbDon't sweat the small stuff.Premium
join:2006-03-04
Calgary, AB | reply to LazMan
How much extra voltage does a DSL connection add too the line? |
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sbrookPremium,Mod
join:2001-12-14
Ottawa
kudos:4 Reviews:
·TekSavvy Cable
·Rogers Hi-Speed
| Nothing worth noting. The reason for a 48V connection for conventional telephones is now largely historical ... The network could be run on significantly lower voltages were it not for all the equipment designed for 48V supervisory currents and 60V+ ringing current.
Amongst other reasons, carbon microphones needed a significant bias current to work properly and with their inherent resistance, voltages over about 40V were required for reliability. Ringers needed 60V plus to make the bells work. The relays and selectors (uniselectors, and 2 motion selectors) in early strowger exchanges worked best with about 48V operating voltages to combine reliability and speed etc. Also, party line selection which was done by grounding a circuit may result in higher resistance completing the circuit.
DSL doesn' add much at all by comparison. |
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LazManPremium
join:2003-03-26
canada | reply to sbrook
said by sbrook:Yeah, hitting him with a megger is NOT a nice idea! You're right - but he didn't seem to understand why we didn't see the humour in the test-call thing, until after the megger thing.... |
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