dpz@dimacs.rutgers.edu (David Paul Zimmerman) (07/26/90)
I've got a floor that is AT&T wired for 4 twisted pair to each office. That includes my office. I needed to get two connections to my office, one serial connection for my PC and one 10baseT for my Sun. It almost looked like I had to do a new 4 pair run for the second connection, but decided to try a hack: In the closet, I punched down 2 pair serial in my now-standard pattern: 1 (jack pin 5) cisco RxD 2 (jack pin 4) cisco TxD 5 (jack pin 3) cisco ring (I don't use it on the DTE but punch anyway) 6 (jack pin 6) cisco ground Then I punched in the Cabletron 10baseT stuff non-standardly: 3 (jack pin 1) normal 4 (jack pin 2) normal 7 (jack pin 7) shifted from 5 (jack pin 3) 8 (jack pin 8) shifted from 6 (jack pin 6) In the room, I took a 4 cubit length of flat 8 conductor (my standard wall-to-computer cabling) and stripped off half the length of outside gray plastic. On the intact end, I crimped a 8 conductor modular normally. On the other end, I crimped 4 of the now-flailing wires normally for serial (3->3, 4->4, 5->5, 6->6). I then crimped the other four to reverse my 10baseT closet hack (1->1, 2->2, 7->3, 8->6). It actually works, if you don't mind looking at it, just don't tug very hard on those modular connectors :-). It certainly saved me the work and cost of another wire run. BTW - yes, if I had thought out my wiring plan a little better four months ago when I started forming my wiring plan, I wouldn't have had to do the shifting. In fact I probably could have also instead just gotten a modular adapter to duplicate the 8 conductor wall socket into two 8 conductor connectors. David -- David Paul Zimmerman dpz@dimacs.rutgers.edu Systems Programmer rutgers!dpz Rutgers Univ Center for Discrete Math and Theoretical Computer Science (DIMACS)
rsmith@vms.macc.wisc.edu (Rusty Smith, MACC) (07/26/90)
In article <Jul.25.22.03.10.1990.17179@dimacs.rutgers.edu>, dpz@dimacs.rutgers.edu (David Paul Zimmerman) writes... >I've got a floor that is AT&T wired for 4 twisted pair to each office. That >includes my office. I needed to get two connections to my office, one serial >connection for my PC and one 10baseT for my Sun. It almost looked like I had >to do a new 4 pair run for the second connection, but decided to try a hack: stuff deleted >In the room, I took a 4 cubit length of flat 8 conductor (my standard >wall-to-computer cabling) and stripped off half the length of outside gray >plastic. On the intact end, I crimped a 8 conductor modular normally. On the >other end, I crimped 4 of the now-flailing wires normally for serial (3->3, >4->4, 5->5, 6->6). I then crimped the other four to reverse my 10baseT closet >hack (1->1, 2->2, 7->3, 8->6). It actually works, if you don't mind looking You may find problems with the flat gray cable. It is not twisted for 10 baseT . We are using Cabletron Equipment and 4 twisted pairs to each office also. When we also need RS232 serial connections we just put a splitter at the office RJ45. The first 2 pairs go to one side, the next 2 pairs the other side of the splitter. Then connect twisted pair interface cables for 10baseT and flat grey to a DB25 modular adapter for the RS232. Radio Shack lists duplex splitters for $4.95, we get them from our supplier for $1.80. This may help as your network grows. Rusty Smith Internet: rsmith@vms.macc.wisc.edu MACC Data Communications Bitnet: rsmith@wiscmacc (608) 263-6307 Univ. of Wisconsin @ Madison
dpz@dimacs.rutgers.edu (David Paul Zimmerman) (07/27/90)
rsmith@vms.macc.wisc.edu (Rusty Smith, MACC) writes: >You may find problems with the flat gray cable. It is not twisted >for 10 baseT . I have, in fact, seen the problems you're referring to, but only in a test situation where I was using a real stupidly long length of the stuff (15 cubits or so). It was great -- we'd plug in the 10baseT xcvr and one by one all the port lights on the central Cabletron TPT-MIMs would go solid. Most of the time, though, I'm using very short lengths, 2 cubits max, with the main length from the wall to the CPU handled by a 3 meter xcvr cable between the CPU and the 10baseT xcvr. The more stupid lengths come into play mainly for serial connections, where I only have the flat gray to go between the wall and CPU, but surprisingly they have also been pretty much uneventful, even the longest ones (~10-12 cubits). >Radio Shack lists duplex splitters for $4.95, we get them >from our supplier for $1.80. This may help as your network grows. Radio Shack sells 8 conductor duplex splitters? Didn't know that -- I'll have to check them out. Who is the other supplier? David -- David Paul Zimmerman dpz@dimacs.rutgers.edu Systems Programmer rutgers!dpz Rutgers Univ Center for Discrete Math and Theoretical Computer Science (DIMACS)