I'm no telco guy, so these aren't answers from first-hand knowledge, but my understanding is... On Fri, Sep 11, 2009 at 8:43 AM, Tony Vandiver wrote: > In my youth, I dug trenches as a contractor for a phone company and put > down a bundle of 4 pvc pipes about 2" in diameter each for fiber optic > lines. =A0My guess is that a lot of the phone line traffic is moving over > fiber without the lossy effects of copper close to the phone company - > further out, your neighbor may not be so lucky. =A0But that's just a guess > - next question is how they transition from fiber to copper, and I don't > have a clue. The have a fiber to copper converter. Each cable also includes power lines (48VDC) to power the converter and any repeaters along the way. Look carefully as you drive around and you'll see these boxes popping up everywhere. > The bigger question to me is how the phone wiring is laid > out vs. cable. =A0Once upon a time I suppose you had one pair of wires > between your house and the pbx, but surely that's not possible now. No, this is still done pretty widely - otherwise DSL wouldn't work. Look at the end of a typical phone cable and you'll see it has hundreds of pairs, all leading back to the branch office. These are falling out of favor due to the cost and other resources required to maintain millions of miles of these. Cheaper to have a pair or two of fiber going to a neighborhood. > Compare that to the early versions of cable that were essentially a > single pair coming from the cable company that branched out to every > house drop. =A0If that were true now, there would have to be one heck of a > lot of traffic on that pair of wires at the cable company for them to > support the same kinds of throughput as DSL for multiple customers - not > to mention on demand hd movies. Cable has a very, very, very high bandwidth capacity. Imagine cramming all the RF spectrum from 3GHz (or higher) down to DC into a single wire. It has its limitations, but at the moment it's not an issue. You get a lot more bandwidth out of a shielded RF cable (which the cable company uses) than an unshielded twisted pair (which the phone company uses). Both, however, are moving towards fiber, and only converting to copper in the neighborhood, or at the house. -Adam -- = http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist