Anyone familiar with Balance and Un-Balanced E1/PRI
Customer is asking....(in regards to Dual E1/PRI) Can you please explain to me whether these should be balanced or unbalanced? I'm asking..Is this dictated by Telco? If so, does the card have the ability to change via software setting or board jumper? Does it even matter to the card set? Steve Rivera IM: srivera711 Toll Free: (877)WRCANET x102 DIRECT: 732-833-2034 Fax available equipment to: (732)833-2115 for more product info got www.wrca.net
First off...sorry for the delay in replying to this...was on vacation last week hiking in Colorado (no, I didn't see any wildfires ;) Didn't see any other responses, so hopefully this will help. Also sprach Stephen Rivera - WRCA.Net
Can you please explain to me whether these should be balanced or unbalanced?
In general usage, a balanced line is a line where the "signal" (analog or digital) is sent on two different wires with opposite polarity (ie, where one has a positive voltage, the other wire will have an equal but negative voltage). This gives greater immunity to RF interference and the like. Unbalanced, of course, being when it only uses a single wire for the signal, and the measurement of the signal is measured relative to ground, thus resulting in less resistance to RF interference. FWIW, ethernet, and traditional 4-wire T1's are balanced signals (2 transmit wires, 2 receive wires, the polarity of the signals on the 2 wires of each type are opposite of each other). DSL is *un*balanced (it only uses 2 wires, so there aren't 4 wires on which to balance the signals). I don't know about how E1's work down at the wire level (being in North America), but I suspect they are balanced. Also, FWIW (this may be getting into more than you wanted to know), the balancing of the signals is why you have the twisting in twisted pair cables. If the wires ran straight side by side (we'll say left and right for example), another wire running to the left of the two wires would induce more signal in the left wire than it would in the right, and screw up the balanced signal (only slightly, but over long runs, it can add up). By twisting the wires together, at one point the other wire will induce more signal on the first wire, but after the twist, it will be inducing more signal on the second wire, offsetting the previous extra induced signal in the first wire...overall this keeps the balanced signal correct over long hauls.
I'm asking..Is this dictated by Telco?
Typically, yeah...whatever the interconnect is, is what you'll need to run, unless you convert it somewhere along the way. I'd be really surprised if it wasn't a balanced line as pretty much all T1's on copper are balanced. (Note, this whole discussion has to do with copper wiring, you don't get RF interference from fiber, so the issue is moot there).
If so, does the card have the ability to change via software setting or board jumper? Does it even matter to the card set?
I've not seen any settings to change this, but haven't had the need to look for it. -- Jeff McAdams Email: jeffm@iglou.com Head Network Administrator Voice: (502) 966-3848 IgLou Internet Services (800) 436-4456
I'm pretty sure T1's are NOT balanced. Think of the tx and rx pairs as two seperate lines, they aren't necessarily bundled together. If it was balanced, you'd see three wires per tx/rx "pair"; you'd have the ground, positive and negative... Haven't seen that (yet). The closest I've seen is a shielded run... -- Charles Sprickman spork@inch.com On Mon, 1 Jul 2002, Jeff Mcadams wrote:
First off...sorry for the delay in replying to this...was on vacation last week hiking in Colorado (no, I didn't see any wildfires ;) Didn't see any other responses, so hopefully this will help.
Also sprach Stephen Rivera - WRCA.Net
Can you please explain to me whether these should be balanced or unbalanced?
In general usage, a balanced line is a line where the "signal" (analog or digital) is sent on two different wires with opposite polarity (ie, where one has a positive voltage, the other wire will have an equal but negative voltage). This gives greater immunity to RF interference and the like. Unbalanced, of course, being when it only uses a single wire for the signal, and the measurement of the signal is measured relative to ground, thus resulting in less resistance to RF interference.
FWIW, ethernet, and traditional 4-wire T1's are balanced signals (2 transmit wires, 2 receive wires, the polarity of the signals on the 2 wires of each type are opposite of each other). DSL is *un*balanced (it only uses 2 wires, so there aren't 4 wires on which to balance the signals). I don't know about how E1's work down at the wire level (being in North America), but I suspect they are balanced.
Also, FWIW (this may be getting into more than you wanted to know), the balancing of the signals is why you have the twisting in twisted pair cables. If the wires ran straight side by side (we'll say left and right for example), another wire running to the left of the two wires would induce more signal in the left wire than it would in the right, and screw up the balanced signal (only slightly, but over long runs, it can add up). By twisting the wires together, at one point the other wire will induce more signal on the first wire, but after the twist, it will be inducing more signal on the second wire, offsetting the previous extra induced signal in the first wire...overall this keeps the balanced signal correct over long hauls.
I'm asking..Is this dictated by Telco?
Typically, yeah...whatever the interconnect is, is what you'll need to run, unless you convert it somewhere along the way. I'd be really surprised if it wasn't a balanced line as pretty much all T1's on copper are balanced.
(Note, this whole discussion has to do with copper wiring, you don't get RF interference from fiber, so the issue is moot there).
If so, does the card have the ability to change via software setting or board jumper? Does it even matter to the card set?
I've not seen any settings to change this, but haven't had the need to look for it. -- Jeff McAdams Email: jeffm@iglou.com Head Network Administrator Voice: (502) 966-3848 IgLou Internet Services (800) 436-4456
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Also sprach Charles Sprickman
I'm pretty sure T1's are NOT balanced. Think of the tx and rx pairs as two seperate lines, they aren't necessarily bundled together. If it was balanced, you'd see three wires per tx/rx "pair"; you'd have the ground, positive and negative... Haven't seen that (yet). The closest I've seen is a shielded run...
Being balanced doesn't require a ground. A ground just means that its grounded. Balanced is just having two signals of opposite polarity and reading the signal as half the voltage differential between the two wires. Unbalanced is reading the signal as the differential between the signal wire (just one) and ground. Ground, in the unbalanced case, can be a local ground, there doesn't have to be a ground in the cable to measure against. In fact, after a cable run, its likely to *not* have the same potential as a real ground as there's a good chance that there will have been current induced in it. -- Jeff McAdams Email: jeffm@iglou.com Head Network Administrator Voice: (502) 966-3848 IgLou Internet Services (800) 436-4456
participants (3)
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Charles Sprickman -
Jeff Mcadams -
Stephen Rivera - WRCA.Net