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Joined: Sep 2005
Posts: 9,289 Likes: 15
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A balanced line is transposed at the end so that any noise on one side is the opposite phase of the other side therefore the noise is canceled out
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Joined: Dec 2005
Posts: 7,056
RIP Moderator-Mitel, Panasonic
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RIP Moderator-Mitel, Panasonic
Joined: Dec 2005
Posts: 7,056 |
Dang, this is gonna be fun. Another way to drop loop current. Silicon diodes! I use 1N4004, but anything rated 400 volts or higher and 1 Amp or better will work fine. BUT, (you knew this was coming didn't you), you have to use them the right way. The idea here is that a silicon diode has a forward voltage drop of 0.7 volts DC. The neat thing is, if it is forward biased, (current flowing the right direction), there is NO AC voltage drop. OK, micromicrovolts, but no drop for all practical purposes. The catch is, you have to connect them inversely in pairs so AC (Voice AND Ringing) can do its AC thing. And you have to put a set on Tip and then a set on Ring to maintain longitudinal balance. So, we put 1 set on Tip, and 1 set on Ring, for a total voltage drop of 1.4 volts and AC is not affected and balance is ok. What have we accomplished is lowering the voltage drop across the co network in the phone system. Lower voltage = lower current. What it looks like electrically, is a DC only resistor. The messy part is, where do you put 10 or more diodes for EACH line. 66m blocks work well, but build in the shop so that it looks neat and pretty. It really does work, but I would use Sandmans stuff if I had to deal with high loop current today. He wasn't around 20-25 years ago. But, if $ is a problem and time is cheap.....
John C.
When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.
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Joined: Sep 2006
Posts: 329
Member
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Member
Joined: Sep 2006
Posts: 329 |
I guess what you're saying is
/----|<-----\ \---->|-----/ or
/----|<-----\ /----|<-----\ \---->|-----/ \---->|-----/ or
/----|<----|<-----|<----\ \---->|---->|----->|----/ on each side.
Is that right?
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Joined: Jul 2003
Posts: 1,235
Member
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Member
Joined: Jul 2003
Posts: 1,235 |
i did get some resistors a little lower than 600 ohms. put one on each side before the ksu. it brought the current down to 30ma and seems to have good volume and rings in ok. going to let the customer use it a day and if everything works well i will do all of them. thank you for all the feedback. dave
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Joined: Sep 2006
Posts: 329
Member
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Member
Joined: Sep 2006
Posts: 329 |
Thanks for reporting in. It's nice to know that some of the "science" we learned in school actually works in the real world.
I am curious how you connected these resistors in. Did you use a beanie or a scotchlock? A picture would be great!
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Joined: Jul 2003
Posts: 1,235
Member
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Member
Joined: Jul 2003
Posts: 1,235 |
i used ur connectors on the c o end. they worked fairly well. if not careful they can shift out of the channel. i punched the other side at the ksu 66 block. the resistor hides neatly behind the plastic guide but the resistor wire doesnt cut real well with a 66 tool. i did end up with a row of 16 ur connectors next to the block.
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Joined: Dec 2005
Posts: 7,056
RIP Moderator-Mitel, Panasonic
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RIP Moderator-Mitel, Panasonic
Joined: Dec 2005
Posts: 7,056 |
MP, you got it exactly. I don't have a scanner, so I was at a loss as to how to show a picture. It's astounding what you can do with all the little characters that I ignore! John C.
When I was young, I was Liberal. As I aged and wised up, I became Conservative. Now that I'm old, I have settled on Curmudgeon.
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Joined: Dec 2006
Posts: 108
Member
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Member
Joined: Dec 2006
Posts: 108 |
From a post I made on the Avaya Forum Can someone explain the weird voltages?
We did some testing today to try to pin it down and found some weird voltages.
Some lines show 48 to 51 volts Tip to ring where others are around 37 to 38 volts, I thought the standard was 48 volts. The 48 to 51 volt lines show about 0.25 volts Tip to ground where the 37 to 38 volt lines show 7 to 8 volts Tip to ground, I thought Tip should always be close to ground.
I also get about 8 volts AC Tip or Ring to ground and 15 Volts on others.
I should mention that some of the lines are direct copper to the CO about 4 mies away and others come from a terminal unit located about 3000 feet away. When direct copper goes bad Verizon usuly switches us to the terminal. A few times when they have done this they failed to option the cards correctly and left us with either a ground start line or a line that would not cut over on ring, it would wait till the ring voltage droped before the call cut over.
Could the weird voltages be card option problems or is this new stuff 37 to 38 volts and not Tip grounded.
The thing that gets me is the 7 to 8 volts tip to ground on some lines.
On the Loop current subject, I have several Adtran Atlas 550's with FXO cards I have found that at 65ma they will open the loop for about 20 seconds every 2 or 3 minutes or so. I droped the loop to 25ma with resistors and the problem went away. You could pull the card right after it droped and the components where very hot, at 25ma they are just warm. I could have tolerated the loss on the AC talk side as I could have adjusted the Adtran to add some gain to the audio but I could see (hear) no change so I left it alone. Wound up adding 1000 ohms tip and 1000 ring.
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