MCARR@auvm.auvm.edu (mike carr) (04/17/91)
Which is better to have and why? An interior modem or external modem? Mike Carr
root@zswamp.uucp (Geoffrey Welsh) (04/18/91)
In a letter to All, mike carr (MCARR@auvm.auvm.edu ) wrote: >Which is better to have and why? An interior modem or >external modem? Internal modems are cheaper because they don't have a case, power supply... or UL/CSA approval (required in Canada for devices which plug into the wall, but not for peripheral cards). External modem advantages: - status lights (I like to know what the modem's doing) - I choose what serial port it plugs into: dumb 8250, 16550, or intelligent multiserial card - doesn't take up a slot in my crowded PC - generated heat is external to my PC - don't have to take apart my PC to reconfigure modems or send them out for service - I don't have to accept the manufacturer's selection of COM port addresses, nor of interrupts (of which my PC is very short) - I can grab an external modem and plug it into my friend's laptop, one of Wilfrid Laurier University's 3B2s or MicroVAX, a multiplexer, etc... -- UUCP: watmath!xenitec!zswamp!root | 602-66 Mooregate Crescent Internet: root@zswamp.fidonet.org | Kitchener, Ontario FidoNet: SYSOP, 1:221/171 | N2M 5E6 CANADA Data: (519) 742-8939 | (519) 741-9553 The mile is traversed not by a single leap, but by a procession of coherent steps; those who insist on making the trip in a single element will be failing long after you and I have discovered new worlds. -- me
tnixon@hayes.uucp (04/18/91)
In article <91106.183103MCARR@auvm.auvm.edu>, MCARR@auvm.auvm.edu (mike carr) writes: > Which is better to have and why? An interior modem or external modem? With an external modem, you have LED indicators, which can help diagnose problems. If there is a problem with your software or something, you can just reach over and turn off the modem's power switch to hang up the phone line, which you can't do with an internal modem without turning off the computer. An external modem is independent of the bus structure of the computer -- you can use it with a Sun, Mac, PC XT, PC AT, EISA, MCA, minicomputer, whatever, and move between those systems at will, while an internal modem only works on a specific system (and when you consider that high-speed modems are still fairly expensive, the ability to continue using it after you upgrade your computer system is important). An external modem doesn't use up a slot in your computer, especially if you already have a built-in serial port that's free. It's much easier to share an external modem between systems using an A/B switch. An external modem doesn't introduce another source of heat and electronic "noise" into your computer. If you want to replace an external modem, get it repaired, or temporarily connect a different modem for testing, it's a cinch. An external modem can easily be changed from async to sync operation and plugged into different kinds of serial ports. If you ever want to use an external device to power up your computer when a call comes in, an external modem can control it but an internal modem can't. An internal modem, on the other hand, doesn't require a cable (which saves a little money), and doesn't take up space on your desk. It's harder to steal, if you're in an area where that's an issue. You also don't have to buy a separate serial card -- but you DO have to worry about the IRQ/address of the modem colliding with built-in serial ports in your system. You don't have another power cord to worry about, and you don't have to worry about finding another AC outlet to plug into. The modem automatically turns on when the PC is turned on. Because an internal modem doesn't have a cabinet or power transformer, it is generally cheaper than an external modem of equivalent capability -- but many high-end modems now come ONLY in external versions, primarily for the portability reasons I cited above. Personally, I prefer external modems, because I'm always doing testing and swapping modems around. You have to decide for yourself based on what reasons are important to you. -- Toby -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net
bill@bilver.uucp (Bill Vermillion) (04/18/91)
In article <7223.280D280F@zswamp.uucp> root@zswamp.uucp (Geoffrey Welsh) writes: >In a letter to All, mike carr (MCARR@auvm.auvm.edu ) wrote: > >Which is better to have and why? An interior modem or > >external modem? > Internal modems are cheaper because they don't have a case, power >supply... or UL/CSA approval (required in Canada for devices which plug into >the wall, but not for peripheral cards). > External modem advantages: And if you get a lightning strike while you are connected to the phone lines with an external modem, the only problem you are likely to have is a dead modem - which brings this line Internal modem disadvantages. If you have a lightning strike nearby when you have an internal modem connected, you have just invited mother nature to be a guest in your machine. I had one client who did that. The net loss, besides the modem, was the mother-board, the video display card and the powersupply. Not cheap. Think of an external modem as a $200 fuse for a $5000 computer :-) -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
greg@gagme.chi.il.us (Gregory Gulik) (04/19/91)
MCARR@auvm.auvm.edu (mike carr) writes: > Which is better to have and why? An interior modem or external modem? Three good reasons off the top of my head: 1) Modems are a pain to set up, and if you screw up, you can flick it off and on to reset it. This is especially true of the newer high speed modems (Telebit, USR, etc...) 2) I like the lights to see what's going on. 3) You can still use it if you change computers. I've used the same 2400 baud modem since I bought my Apple //e years ago. Since then I used it on a Zenith PC, and now it's on one of the dial-up lines on my 3B2. Can't do that with an internal!!!!! -greg -- Gregory A. Gulik Call Gagme, a public greg@gagme.chi.il.us || ...uunet!motcid!gulik access UNIX system at || gulik@depaul.edu (312) 714-8568
neal@mnopltd.UUCP (04/20/91)
->Which is better to have and why? An interior modem or external modem?
->
->Mike Carr
I vote for exterior modems everytime:
- Lights show me what it is doing;
- I can move it from one machine to the next;
- I avoid funky bugs in various unix's;
- I get to spend more money.
But then I do a lot of configuration and testing, and the above stuff is
important.
------------------------------------------------------------------------------
Neal Rhodes MNOP Ltd (404)- 972-5430
President Lilburn (atlanta) GA 30247 Fax: 978-4741
emory!mnopltd!neal
------------------------------------------------------------------------------tnixon@hayes.uucp (04/22/91)
In article <1991Apr18.162946.29336@bilver.uucp>, bill@bilver.uucp (Bill Vermillion) writes: > And if you get a lightning strike while you are connected to the phone > lines with an external modem, the only problem you are likely to have is a > dead modem - which brings this line > ... > If you have a lightning strike nearby when you have an internal modem > connected, you have just invited mother nature to be a guest in your > machine. > ... > Think of an external modem as a $200 fuse for a $5000 computer :-) I specifically didn't include this widely-held view in my list of advantages/disadvantages. Why? Because lighting is so unpredictable and dangerous. I've seen several cases of lighting going THROUGH an external modem, arcing all around inside, and into the computer through the EIA-232 cable, so I can't list "lighting protection" as an advantage of external modems. It may help a little, but it's no guarantee. You need external protection, whether your modem is internal or external. -- Toby -- Toby Nixon, Principal Engineer | Voice +1-404-840-9200 Telex 151243420 Hayes Microcomputer Products Inc. | Fax +1-404-447-0178 CIS 70271,404 P.O. Box 105203 | UUCP uunet!hayes!tnixon AT&T !tnixon Atlanta, Georgia 30348 USA | Internet hayes!tnixon@uunet.uu.net
jsr@dexter.mi.org (Jay S. Rouman) (04/23/91)
In article <3921.2812b277@hayes.uucp> tnixon@hayes.uucp writes: >unpredictable and dangerous. I've seen several cases of lighting >going THROUGH an external modem, arcing all around inside, and into >the computer through the EIA-232 cable, so I can't list "lighting >protection" as an advantage of external modems. It may help a >little, but it's no guarantee. You need external protection, >whether your modem is internal or external. Just the kind of reassuring words we wanted to hear during lightning season. ;-) What's considered good external protection these days? Will MOV's across the line do the job? There are tons of places selling phone line protection devices but you never know what's inside or if they have much chance of working. -- Jay S. Rouman Voice: 517/773-7887 | Distrust education. Two of E-mail: jsr@dexter.mi.org | the three R's are misspelled.
bdb@becker.UUCP (Bruce D. Becker) (04/23/91)
In article <91106.183103MCARR@auvm.auvm.edu> MCARR@auvm.auvm.edu (mike carr) writes: |Which is better to have and why? An interior modem or external modem? External is much better since you can get a computer with a more reasonable hardware architecture, and still have use of the modem... -- ,u, Bruce Becker Toronto, Ontario a /i/ Internet: bdb@becker.UUCP, bruce@gpu.utcs.toronto.edu `\o\-e UUCP: ...!utai!mnetor!becker!bdb _< /_ "Waking up is hard to do" - Neil Sedated
root@zswamp.uucp (Geoffrey Welsh) (04/23/91)
In a letter to All, Jay S. Rouman (jsr@dexter.mi.org ) wrote: >What's considered good external protection these days? >Will MOV's across the line do the job? There are a lot of places that'll sell you a device with one MOV accross the hot and neutral lines; however, you want 120V MOVs between hot and netural and between hot and ground, and a much lower (30V?) MOV between neutral and ground. Unfortunately, there is no way to test if an MOV is still working, short of trying it... which might kill it and you wouldn't know until the next surge came along! Careful choice of fuse *might* also help. DISCLAIMER: power transmission engineering was never my specialty. -- UUCP: watmath!xenitec!zswamp!root | 602-66 Mooregate Crescent Internet: root@zswamp.uucp | Kitchener, Ontario FidoNet: SYSOP, 1:221/171 | N2M 5E6 CANADA Data: (519) 742-8939 | (519) 741-9553 The mile is traversed not by a single leap, but by a procession of coherent steps; those who insist on making the trip in a single element will be failing long after you and I have discovered new worlds. -- me
chip@osh3.OSHA.GOV (Chip Yamasaki) (04/24/91)
In <1368@gagme.chi.il.us> greg@gagme.chi.il.us (Gregory Gulik) writes: >MCARR@auvm.auvm.edu (mike carr) writes: >> Which is better to have and why? An interior modem or external modem? >Three good reasons off the top of my head: >1) Modems are a pain to set up, and if you screw up, you can flick it > off and on to reset it. This is especially true of the newer > high speed modems (Telebit, USR, etc...) Furthermore, if you occasionally move your phone line from modem to phone to fax (I know, tacky) the back of your computer may not be a convenient place to reach. >2) I like the lights to see what's going on. Indispensible for debugging. >3) You can still use it if you change computers. I've used the same > 2400 baud modem since I bought my Apple //e years ago. Since then > I used it on a Zenith PC, and now it's on one of the dial-up lines > on my 3B2. Can't do that with an internal!!!!! Not only changing computers, but also to drive a terminal or printer. If you have a single Laser printer to serve several computers one option might be programmable autodial modems and an external modem on the computer. SCO Unix is supposed to be able to handle this. One important point that Greg left out was that some people REFUSE to use internal modems (or other devices that can be external) because they restrict the air-flow and create more heat in the PC case. This way the modem can fry your other boards (including motherboard) while it bakes itsself. -- -- Charles "Chip" Yamasaki chip@oshcomm.osha.gov -- -- Charles "Chip" Yamasaki chip@oshcomm.osha.gov
kaufman@neon.Stanford.EDU (Marc T. Kaufman) (04/24/91)
In article <7244.2815110B@zswamp.uucp> root@zswamp.uucp (Geoffrey Welsh) writes: >In a letter to All, Jay S. Rouman (jsr@dexter.mi.org ) wrote: - >What's considered good external protection these days? - >Will MOV's across the line do the job? > There are a lot of places that'll sell you a device with one MOV accross >the hot and neutral lines; however, you want 120V MOVs between hot and >netural and between hot and ground, and a much lower (30V?) MOV between >neutral and ground. Unfortunately, many line sockets are miswired, so you 30V MOV stands a good chance of being placed across 120V. And since 120V is "nominal" RMS, you probably REALLY want about 200V (135 x 1.414 + safety). And anyway, MOVs won't do much for lightning strikes that are close -- you need spark gaps for that. Marc Kaufman (kaufman@Neon.stanford.edu)
bill@bilver.uucp (Bill Vermillion) (04/24/91)
In article <3921.2812b277@hayes.uucp> tnixon@hayes.uucp writes: >In article <1991Apr18.162946.29336@bilver.uucp>, bill@bilver.uucp >(Bill Vermillion) writes: >> And if you get a lightning strike while you are connected to the phone >> lines with an external modem, the only problem you are likely to have is a >> dead modem - which brings this line >> ... >> If you have a lightning strike nearby when you have an internal modem >> connected, you have just invited mother nature to be a guest in your >> machine. >> ... >> Think of an external modem as a $200 fuse for a $5000 computer :-) > >I specifically didn't include this widely-held view in my list of >advantages/disadvantages. Why? Because lighting is so >unpredictable and dangerous. I've seen several cases of lighting >going THROUGH an external modem, arcing all around inside, and into >the computer through the EIA-232 cable, so I can't list "lighting >protection" as an advantage of external modems. It may help a >little, but it's no guarantee. You need external protection, >whether your modem is internal or external. I suspect you see more than your fair share of dead modems coming from "south of YOUR border". The last week we have had tremendous storms - almost on a continuing basis. From experience - yes - lighthing will do strange and unpredictable things. But in the largest majority of cases lightning strikes that induce voltages into the phone system will damage a modem, but only seldom will they go past that. Locally, in my circle of acquaintences I have not seen a damaged computer with an external modem. The worst I have seen is the transceiver chips on the serial port go too. On the other hand one machine I know of had an internal modem. It took out the motherboard, the powersupply, the video display card, and the modem. I have had three modems become inoperative because of lightning hits. (not too bad for operating 24 hours per/day for 10 years here in the lighthing capitol of America). Machines never faltered. The last problem was induced voltage caused by a hit about 75 feet away that stripped the bark to the ground on a 75 foot tall pine tree. The Trailblazer stopped answering the phone, although it thought it was. Turned out the problem was the relay that takes it on/off line. The phone lines have gas-discharge devices entering the house. It's just a rule of thumb in this area never to put in an internal. Particularly if you are going to be using it any amount of time. Sometimes the first indication you have a storm in this area is the thunder. If you say not use it when there is chance of storms the best thing is to unplug the modem in April and plug it back in in November. Average is well over 150 thunderstorms per year in this area ( a strip about 200 miles wide from Tampa bay to Cape Canaveral) -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
larry@nstar.rn.com (Larry Snyder) (04/25/91)
SAM's here had 2400 baud internal modems for $66 - and they
appear to work quite well.
I was thinking of picking up 6 of these modems, throwing them
in a box with an ethernet board and a small (40 meg hard drive)
then attaching them to the network as a terminal server --
But then I remembered my days of living in Orlando - where I
lost 2 modems one summer (both 100% hayes "Smartmodem 2400"
externals)...
--
Larry Snyder, NSTAR Public Access Unix 219-289-0287 (HST/PEP/V.32/v.42bis)
regional UUCP mapping coordinator
{larry@nstar.rn.com, ..!uunet!nstar.rn.com!larry}bill@bilver.uucp (Bill Vermillion) (04/25/91)
In article <1991Apr23.001558.5462@dexter.mi.org> jsr@dexter.mi.org (Jay S. Rouman) writes: >In article <3921.2812b277@hayes.uucp> tnixon@hayes.uucp writes: >>unpredictable and dangerous. I've seen several cases of lighting >>going THROUGH an external modem, arcing all around inside, and into >>the computer through the EIA-232 cable, so I can't list "lighting >>protection" as an advantage of external modems. It may help a >>little, but it's no guarantee. You need external protection, >>whether your modem is internal or external. >Just the kind of reassuring words we wanted to hear during lightning >season. ;-) What's considered good external protection these days? >Will MOV's across the line do the job? There are tons of places >selling phone line protection devices but you never know what's inside >or if they have much chance of working. First thing to do is make sure your incoming lines are protected. Locally United has been using gas-discharge tubes for years. So.Bell started later - probably after seeing the lower failure rates for equipment in United. Before these were available we were buying them locally and installing them ourselves. When I was having lighting damage to such things as phone answering devices a few years ago, I had telco replace the carbon blocks on in-coming line with gas discharge - and it cured that problem. Local hits however may get through everything. There is one company here in Fl (and I forget the name) that I talked with that does total protection of incoming lines. Had a site that the lightning entered through the phone lines, got into the ground system, then came back that way and wiped out 5 terminals and all the serial ports on the CPU and totally destroyed 2 printers. If the phone lines had been protected it MIGHT have limited the damage. Hit was on a pole behnd the building. You live here, you get used to it. I have been within 100 feet of strikes numerous times. The tree at a neighbors that bit the telebit. The tree 10 feet from the back door. Gawd that was loud. You do your best, protect as best as you can, and make sure your insurance covers lightning. But gas discharge tubes seem to be a good start. Also check to make sure your lightning protection equipment is good and dies in a fail safe mode. In other words, if it gets hit, it should not stop working. I have seen some that will die during a hit and then you have not protection , but you don't know it. An ovelooked source in many designs is ground strike. That is when it hits near your house, and comes in through your ground system and out through the power lines. This is reverse of what most people think. It does not always come IN through the power lines, and in ground strikes it can EXIT through the power lines. And make sure your grounds are good. -- Bill Vermillion - UUCP: uunet!tarpit!bilver!bill : bill@bilver.UUCP
mikea@chinet.chi.il.us (Mike Andrews) (04/28/91)
In article <1991Apr25.164452.1129@bilver.uucp> bill@bilver.uucp (Bill Vermillion) writes: >In article <1991Apr23.001558.5462@dexter.mi.org> jsr@dexter.mi.org (Jay S. Rouman) writes: >>In article <3921.2812b277@hayes.uucp> tnixon@hayes.uucp writes: >>>unpredictable and dangerous. I've seen several cases of lighting >>>going THROUGH an external modem, arcing all around inside, and into >>>the computer through the EIA-232 cable, so I can't list "lighting >>>protection" as an advantage of external modems. It may help a >>>little, but it's no guarantee. You need external protection, >>>whether your modem is internal or external. > >>Just the kind of reassuring words we wanted to hear during lightning >>season. ;-) What's considered good external protection these days? >>Will MOV's across the line do the job? There are tons of places >>selling phone line protection devices but you never know what's inside >>or if they have much chance of working. > >First thing to do is make sure your incoming lines are protected. >Locally United has been using gas-discharge tubes for years. >So.Bell started later - probably after seeing the lower failure >rates for equipment in United. > >Before these were available we were buying them locally and >installing them ourselves. > >When I was having lighting damage to such things as phone answering >devices a few years ago, I had telco replace the carbon blocks on >in-coming line with gas discharge - and it cured that problem. You can order gas discharge tubes that thread right in to replace the carbons on the protector on your phone lines (where the phone lines enter the house). Check that the ground used by the phone company is a good one, not loose or connected to a rusty electrical conduit. The gas discharge tube replacements are avavailable from North Supply in Lenexa, Kansas. It's better if you can get your local telco to install gas-discharge tubes for you since you're not supposed to mess with that side of your phone service. >Local hits however may get through everything. > >(TEXT DELETED) > >But gas discharge tubes seem to be a good start. >(TEXT DELETED) > >And make sure your grounds are good. Great advice!! Ground your surge suppressors to a SOLID #10 A.W.G. wire with a good connection to a copper cold water pipe or ground stake. Lightning travels on the surface of the wire due to its high frequency, so the larger the diameter of the wire, the better. Don't depend on the grounds in the electrical system or conduits. To test for a good ground reference use an Ohmmeter (VOM). Test the resistance between two proposed ground points. When you find two with less than a few Ohms of resistance between them, you've found good grounds. In a previous life I worked in the security system business. The early microprocessor-based control panels often died in less than a year in our Midwest installations. The makers on the west coast hadn't discovered lightning yet. Often these panels had a phone line connection less than an inch from a power connection. Now all of the makers have a terminal on the panel marked "Earth Ground" connection along with detailed instructions on just what that means.