alan@oetl.UUCP (Alan Strassberg) (11/04/88)
Suggestions needed: I would like to use an EGA display
and a composite monitor at the same time (to monitor
the same display, one locally, one remotely) - so
1. Any problems in doing this ?
2. Suggestions for EGA/composite card that will work
3. Unforseen problems ?
Thanks !
alan
--
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
Alan Strassberg UUCP: ..!{pyramid,leadsv}!oetl!alan
work (408) 425-6126 alan@oetl (alan@leadsv)
=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-doc@holin.ATT.COM (David Mundhenk) (11/05/88)
In article <401@oetl1.oetl.UUCP>, alan@oetl.UUCP (Alan Strassberg) writes: > > Suggestions needed: I would like to use an EGA display > and a composite monitor at the same time (to monitor > the same display, one locally, one remotely) - so > > 1. Any problems in doing this ? > 2. Suggestions for EGA/composite card that will work > 3. Unforseen problems ? I have done this with a no-brand CGA card, but only at a short distance from the CPU. Of course, the resolution wasn't exactly beautiful on the composite. I think you will need a good, shielded cable for remote. Anyway, if it works with a cheap CGA card, it should work with EGA as long as it has composite port. I have one now -- maybe I'll try it! -Dave "Credo quia absurdum" ------------------------------------------------------------------ /^, , , . . , , , , , / } _, , , . __/ | /| / /| /| , , __, __/ /_ _, __, /_ /_./ (_l |/ / /_/ |/ |/. / |/ | /_/ / / /_/ / / /_ / / /\ Disclaimer: My opinions do not reflect those of anyone I work for or with, or anyone who does not look like me.
wew@naucse.UUCP (Bill Wilson) (11/08/88)
From article <401@oetl1.oetl.UUCP>, by alan@oetl.UUCP (Alan Strassberg): > > Suggestions needed: I would like to use an EGA display > and a composite monitor at the same time (to monitor > the same display, one locally, one remotely) - so > > 1. Any problems in doing this ? > 2. Suggestions for EGA/composite card that will work > 3. Unforseen problems ? > You will not be able to run the two monitors at the same time. The reason for this is that the two graphics boards will more than likely be contending for the same graphics memory space. I have seen this problem and the only way you can have two cards in the same machine that I know of is if they are a monochrome and a graphics card. -- Bill Wilson (Bitnet: ucc2wew@nauvm) Northern AZ Univ Flagstaff, AZ 86011 {These views are mine and do not necessarily reflect those of my employer}
freudent@cmcl2.NYU.EDU (Eric Freudenthal) (11/12/88)
From article <401@oetl1.oetl.UUCP>, by alan@oetl.UUCP (Alan Strassberg): > > Suggestions needed: I would like to use an EGA display > and a composite monitor at the same time (to monitor > the same display, one locally, one remotely) - so > > 1. Any problems in doing this ? > 2. Suggestions for EGA/composite card that will work > 3. Unforseen problems ? > I read your question as: "I want to attach two seperate monitors to the same display card to display the same thing at the same time." If that is your question, the answer is definately yes, although I suspect that you do not want to use EGA: It is absoultely imperative that both monitors are capable of running at the same scan rate. (HI-RES ega is at a different scan rate than standard composite). There are other reasons to not choose a high-res interface including high frequency transmission line factors. Your easiest solution is to buy a CGA card which has both a composite (NTSC) output (RCA plug) as well as a 9-pin cga monitor connector because you will not have to buy any special splitters and all the parts are available off-the-shelf. You will not have any memory space contentions if you only have one card in the system which is driving both monitors. In order to get the full resolution of cga displayed on the remote (composite) monitor, you must be very careful about the transmission line: it should have an impedance of 75 ohms (buy RG-59/U cable), and your remote monitor should terminate the line to 75 ohms (any good monitor either has only one composite video input connection which is terminated (check) or has two composite video connections (in, out) and a terminate switch...these are for hooking up a bunch of monitors to the same signal; the last should be terminated). Use proper connectors for everything (NO F CONNECTORS!), and no splices in the line! For maximal resolution, your remote monitor should be a black & white (monochrome), RS-170 (the monochrome part of NTSC) compatible, and capable of displaying 640 lines (sometimes labeled 80 columns). I am serious about monochrome, I stronglly suspect that composite color will be much too blurry to be useful to read any 80 column text. The transmission line is available at most good quality radio stores. I suggest that you buy a pre-made one with BNC connectors on the end, and buy a bnc->rca adaptor for the CGA card; most good monitors have bnc inputs. Don't worry about wire lengths (up to 100') as long as 1) the line is REALLY 59/u (read it on the side of the cable) and terminated properly at the monitor end to 75 ohms. 2) your ground is quiet (doesn't hum; hard to explain). If you are not sure and want to really do this right, buy a monitor which has 'differential' inputs (I haven't bought one in years; if you are having trouble, check with RCA and Motorola) . This means that it electrically isolates the shield on the transmission line from its local ground in a manner which eliminates ground currents (you will see the resulting hum as a slowly moving horizontal bar) in a manner which does not pose a safety hazard. A more dangerous approach which often solves this problem is to make certain that the monitor has no connection to ground (through its case and third prong on its power plug) except through the shielded cable, but this is a bad idea because it may pose a hazard of electrocution if there is a large ground differential between the two locations. (I have seen 100 volts when a radio studio was improperly wired). Of course, as always, when connecting a cable between rooms which you may not know the wiring of, you should be careful not to ground your body, and to use one (preferably insulated) hand at a time.