From: Daan Goedkoop <[EMAIL PROTECTED]> Date: Fri, 9 Jul 2004 21:52:19 +0200
On Friday 09 July 2004 14:46, Jacobson wrote:> Does that mean that the 50V on the phone jack is no problem for these > localtalk boxes, so you don't have to disconnect the phone > system first?
Daan,
I do not THINK so Those boxes allowed to use telephony CABLING (cheap and available), But not the thelephone CABLE (where the phone signal is) I think this cabling was called 'cheapertalk' compared to the real localtalk. (please, do not flame me if I am wrong, its so long ago)
So, (if I am correct) you can use the CABLES, but without the phone signal (you must disconnect the cables from the phone system)
Thank you. Yet the best way to know whether it works is to try it out :-) It does work, neither the serial ports nor the boxes are blown up as the adapter seems to use two pins that don't have 50V on it. Yet when I picked up the phone during the Mac copying files, I heard a clear prprprpprpr noise, so it's indeed a better idea not to connect the localtalk boxes to the telephone. Luckily, the two telephone jacks that I use can be disconnected really easily.
The noise you hear is probably caused by induction. A current in a nearby wire will induce a sympathetic current in wires nearby. The induction falls off as the square of the distance between the wires, but you can't get much closer together than the four wires bundled together in a phone cable (or the eight in an ethernet cable). When I ran my PhoneNet network on the yellow & black wires of my apartment, I could hear a "buzz pause buzz pause buzz" on the phone when I was printing.
Because of induction, it is always better to have a dedicated cable. But the beauty of PhoneNet is/was that you could do it on the cheap without installing additional cableing if your house was wired properly for telephony. You'd have to put up with some cross-talk (inductive interference) but the price was right.
Telephone cables are four wires, two pairs. One pair of wires is green and red. The other pair is yellow and black. Modern telephone systems use only the green and red wires. PhoneNet adapters are configured to make their connection to the yellow and black pair of wires. So, in theory, it is possible to run PhoneNet over existing phone lines in a home or office.
There are a few complicating factors. First, some installations may make use of the yellow and black wires to support a second phone line rather than running a second cable. You wouldn't want to try to use such a yellow/black pair for your PhoneNet installation.
Second, obviously, the yellow and black wires of one extension must be connected to the yellow and black wires of the other extensions in order for PhoneNet to work between those locations in the house. But in the places where only the red and green wires are used for the telephone, the installer usually does not connect the yellow and black wires to anything in the junction box, because it is just an unused pair of wires.
You can correct the latter problem by going to the box where your telephone wires gather and wiring together the yellow wires and wiring together the black wires.
Third, some phone cables made to go between the wall jack and the phone completely lack the yellow & black pair and only have the green & red pair and so won't work for PhoneNet at all. This is particularly common in the six foot phone cables that are often included with modems. I once spent a couple of hours trying to troubleshoot a PhoneNet problem caused by one of these cables...
LocalTalk/PhoneNet also runs great over Cat. 5 and Cat. 3 cabling and the RJ-11 plug of a normal telephone will plug into an RJ-45 jack of Cat. 5 or Cat. 3, connecting to just the middle four wires. So, if you're in a place with ethernet cabling and your computer only supports LocalTalk, it is possible to use LocalTalk over ethernet cables which are not in use for ethernet. Of course, one must set things up in the wiring closet so that PhoneNet connects to PhoneNet, etc.
If one is in need of phonenet boxes it may also be worthwhile to check the non-Apple sections of computers and networking on Ebay. I saw an auction for something like 150 phonenet boxes starting at $10 or $20 a year or so ago. I doubt that happens every day, but every now and then...
Jeff Walther
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