wdw@aucs.UUCP (02/09/87)
Most of the terminals on our campus are presently connected to the wall
with four-prong plugs. We are considering wiring new terminals with
either four-wire or six-wire modular jacks. If anyone has had bad
experiences with these connectors I'd appreciate hearing your warnings.
In particular are these connectors any more sensitive to noise than
what we have been using.
Many thanks.
--
UUCP: {seismo|watmath|utai|garfield}!dalcs!aucs!wdw
BITNET: {wdwvax|wdw}@Acadia
Internet: {wdwvax|wdw}%Acadia.BITNET@WISCVM.WISC.EDUed@mtxinu.UUCP (02/10/87)
>Most of the terminals on our campus are presently connected to the wall >with four-prong plugs. We are considering wiring new terminals with >either four-wire or six-wire modular jacks. If anyone has had bad >experiences with these connectors I'd appreciate hearing your warnings. >In particular are these connectors any more sensitive to noise than >what we have been using. We've been using modular hardware for terminals for a few years, with no ill effects. The modular gear shouldn't be any more noise-prone than other connectors. I offer two cautions, however. First, modular connectors are not very robust mechanically - they don't stand up well to repeated insertion/removal cycles. Second, there is no standard way in which they're wired, so care in desigining the system is needed. In particular, be careful of polarity reversals: standard modular-to-modular cables put a half twist in each pair. Also, the connections are paired from the middle out, so that 4- and 6-wire systems can be made compatible: ----- 6wire ----- -- 4wire -- C1 B1 A1 A2 B2 C2 I recommend using a standard cabling model, and building the connectors at the modular-to-DB25 end in two or three different ways to make the connections work the way you want. -- Ed Gould mt Xinu, 2560 Ninth St., Berkeley, CA 94710 USA {ucbvax,decvax}!mtxinu!ed +1 415 644 0146 "A man of quality is not threatened by a woman of equality."
wayne@fmsrl7.UUCP (02/11/87)
In article <299@mtxinu.UUCP> ed@mtxinu.UUCP (Ed Gould) writes: >>Most of the terminals on our campus are presently connected to the wall >>with four-prong plugs. We are considering wiring new terminals with >>either four-wire or six-wire modular jacks. If anyone has had bad >>experiences with these connectors I'd appreciate hearing your warnings. > >I offer two cautions, however. First, modular connectors are not very >robust mechanically - they don't stand up well to repeated >insertion/removal cycles. Second, there is no standard way in which >they're wired, so care in desigining the system is needed. In the department I do work for here at Ford, we are using RJ-45 connectors (8 line modular) for our serial communications. Here is the wiring layout: Revised RJ45 standard (Version 1R5 09/24/86) Black RJ45 DB Gray RJ45 RJ 11 RJ 12 RJ 45 DTE DCE 25 DCE DTE I/O Name ----- ----- ----- ------ ------ -- ------ ------ --- ----------------- 1 Blue Gray 5 Blue Orange IN - Remote receive OK 1 2 Orange Brown 8 Brown Gray IN - Remote device up 1 2 3 Black Yellow 3 Green Red IN - Data in 2 3 4 Red Green 7 Yellow Black - Ground 3 4 5 Green Red 7 Black Yellow - Ground 4 5 6 Yellow Black 2 Red Green OUT - Data out 6 7 Brown Orange 20 Gray Brown OUT - Local device up 8 Gray Blue 4 Orange Blue OUT - Local recieve OK You may ignore the color codes, these are for RJ-45/RS232 connectors purchased from Black Box (412) 746-5530 $9.95@. Reasoning behind this layout: 1) Using crossed wiring, ANY two devices may be connected. Snap a cable between 2 terminals and they talk, no need to locate a null modem cable. Note that we do not use "straight through" cables (what most people recommend for computers). If you have spent as many hours fighting RS232 "standard connections" as I have, you will appreciate the joy inherent in this. 2) If all you need is TD, RD and ground, all you need is 4 line cable (RJ-11). Cheap, cheap :-) 3) If you need only TD, RD and devices available, you can use 6 line cable (RJ-12). Inexpensive. 4) If you need hardware handshaking, 8 line cable (RJ-45) will do it all. 5) The DB25 connections above are advisory, not absolute. The connector is responsible for having the appropriate signals on the correct RJ lines. Bolt the things on so they become part of the device. 6) Black Box also sells DB-9/BJ45 connectors so we can make PCs conform as well. The time savings in using this system is enormous. The only waste is the 2 ground lines in the center. We have been using this for some time with no problems (the latest revision was for color codes, Black Box changed the order of the colors). If you have any questions, feel free to mail or call me. For all the people who worry about ignorant people coming around and connecting our data lines to the phone company: - We generally keep everything plugged in so there are no open lines or ports to use. - With the number of cables we have, even the telephone repair men are intimidated. - We try to restrict access to authorized people. - If you are going to use wall jacks, I suggest that you label them so that people know better than to plug their phone in. -- ===== Your life is your own fault! ============== Rebel or be oppressed! ===== Michael R. Wayne (313) 322-3986 UUCP: {epsilon|ihnp4}!mb2c!fmsrl7!wayne Working at (but not employed by) Ford Motor Company ** This space for rent ** Since I am an independent consultant, the above opinions ARE my employers. ===== Are your moral/ethical/religious/political beliefs really rational? ====
rhorn@infinet.UUCP (02/17/87)
The growing popularity of using the RJ series connectors (aka
`telephone modular jacks') for terminal cabling is exposing a lot of
people to a major risk. These jacks are directly interchangable with
normal telephone jacks, and you can be sure that people will make
mistakes and plug terminals into telephone equipment. This can do
tremendous damage, and may even pose a health risk.
When a telephone rings, the ring signals are a pulsed DC that can
reach as high as 150 volts! In terms of vaporized semi-conductors,
this is just as destructive as plugging your connector into an electric
outlet. The frequency, voltage, and power don't quite match standard
electric power but they are more than enough to totally destroy any
unprotected electronics.
The health risk arises from the potentially poor grounding of the
digital electronics. These circuits are not normally designed to be
safe with 150 volts on them. This risk may be shortlived since the
digital circuit will quickly self destruct. Telephone extension
cables with RJ connectors pose a greater hazard. When the phone rings
there is high voltage on that connector. If a child is chewing on it
when the phone rings there is a real risk of death from electrocution.
(The hazard to adults is lower since they don't normally chew on
cables, and the power levels are low enough that the odds are in favor
of a nasty jolt instead of fatal one.)
Beware of using these connectors in inappropriate circumstances. (I
was warned quite thoroughly by our Mechanical Design people when I
suggested it. I learned then for the first time that telephones are
not UL approved, nor will they ever be, because of this 150 volt
risk.)
--
Rob Horn
UUCP: ...{decvax, seismo!harvard}!wanginst!infinet!rhorn
Snail: Infinet, 40 High St., North Andover, MAzemon@felix.UUCP (02/21/87)
In article <625@infinet.UUCP> rhorn@infinet.UUCP (Rob Horn) writes: >The growing popularity of using the RJ series connectors (aka >`telephone modular jacks') for terminal cabling is exposing a lot of >people to a major risk. These jacks are directly interchangable with >normal telephone jacks, and you can be sure that people will make >mistakes and plug terminals into telephone equipment. This can do >tremendous damage, and may even pose a health risk. You're absolutely right. I solved this by using RJ-45 sockets/plugs for my terminal equipment. The RJ-45 is 8 pins wide instead of the 4 on the RJ-11. This allows a *really* dumb user to plug his telephone handset in the computer wiring but the terminal plug is physically too large to be inserted into the telephone wiring socket. I like this wiring solution. I kept all the advantages of the modular phone wiring and avoided the electrical hazards. The only disadvantage I have heard of is that the RJ-45/RJ-11 plugs don't have much of a duty cycle life. But I don't really care. They hardly ever get unplugged and if one ever breaks, a new plug costs me about $.25 and takes about one minute to crimp on. -- -- Art Zemon FileNet Corporation Costa Mesa, California ...!hplabs!felix!zemon