Path: utzoo!telecom-request Date: 8 May 91 12:46:29 GMT From: Bob Schreibmaier Newsgroups: comp.dcom.telecom Subject: Re: RJ Wiring for AT&T 258A Message-ID: Organization: QRM Central, Middletown, NJ Sender: Telecom@eecs.nwu.edu Approved: Telecom@eecs.nwu.edu X-Submissions-To: telecom@eecs.nwu.edu X-Administrivia-To: telecom-request@eecs.nwu.edu X-Telecom-Digest: Volume 11, Issue 347, Message 9 of 10 Lines: 68 > Can anybody out there post the definitive method of pairing (with > color code) for the AT&T PDS scheme? I saw a post in comp.dcom.lans > that gave the following diagram: > WH OR WH BL WH GR WH BR > OR WH GR WH BL WH BR WH > (RJ-45F) 1 2 3 4 5 6 7 8 > | | | | | | | | > pairs: T2 R2 T3 R1 T1 R3 R4 T4 > +--+ | +--+ | +--+ > +--------+ > The trouble I have is with pair 4. Which pin is really tip, and > shouldn't it be white/brown? Also, is pair 2 really on pins 1 and 2, > or is it on 3 and 6? I used to work on PDS about umpteen years ago (back when I had a job!). Let's see if my memory serves correctly. If I can map the pins assignments on the 8-pin jack to where they go on a 110A connector block (replacement for the old 66 blocks) we can get this right. It's a very strange mapping and I have no idea about where it came from historically. The 110A block actually is easier to understand in that it is laid out as tip-ring pair 1, tip-ring pair 2, tip-ring pair 3, and tip-ring pair 4. Like so: 1 2 3 4 5 6 7 8 | | | | | | | | 110A block T1 R1 T2 R2 T3 R3 T4 R4 The mapping of the eight-pin modular jack to 110A is: 8-pin 110A 5 (T1) 1 4 (R1) 2 1 (T2) 3 2 (R2) 4 3 (T3) 5 6 (R3) 6 7 (T4) 7 8 (R4) 8 So, actually, Tip of pair 4 is on pin 7 and Ring is on pin 8. In the PDS wiring scheme, pair 4 is typically used for powering of adjuncts via a power supply either connected locally or placed in a satellite closet. Usually had -48 volts on pin 7 and ground on pin 8. However, it was also used with the 355B and 355BF protective adapters for RTS/CTS hardware flow control with the AIM4 boards on the AT&T Information Systems Network packet data switch (if you have any interest). Lessee now ... regarding your question of color codes, I believe you have them right, but my memory is foggy on that one. But your pairing is correct. Pins 4-5 are pair 1, pins 1-2 are pair 2, pins 3-6 are pair 3, and pins 7-8 are pair 4. I sure hope this helps rather than confuses more! Bob Schreibmaier K2PH | UUCP: ...!attmail!dxis!k2ph a.k.a. "The QRPer" | Internet: k2ph@dxis.attmail.com Middletown, New Jersey | ICBM: 40o21'N, 74o8'W