akcs.larry@nstar.UUCP (Larry Snyder) (10/19/89)
What is the longest one could build a keyboard/monitor extension cable for a VGA or EGA monitor and have it work without damaging any of the equipment? Could it be 40 feet long? 50 feet? The reason I ask is that I am considering moving my monitor and keyboard downstairs and will need around 50 feet of cable for both the AT keyboard and monitor.
unkydave@shumv1.uucp (David Bank) (10/19/89)
In article <[253d2160:289]comp.sys.ibm.pc@nstar.UUCP> akcs.larry@nstar.UUCP (Larry Snyder) writes: >What is the longest one could build a keyboard/monitor >extension cable for a VGA or EGA monitor and have it work >without damaging any of the equipment? > >Could it be 40 feet long? 50 feet? > >The reason I ask is that I am considering moving >my monitor and keyboard downstairs and will need around >50 feet of cable for both the AT keyboard and monitor. Well, the keyboard is essentially a serial device. A "typical" serial port (let me know when you find one) can drive about 100 feet without any noticeable loss of signal. After that you start getting degredation and you'll eventually lose the signal somewhere between 300 and 500 feet. That still doesn't answer your question, does it?? Depending on how well built the PC is, and what quality of components went into it, I'd say you have about an 80% chance of doing what you want with the keyboard....assuming "normal"-quality components. Damage to the keyboard is not a concern here. Now, the monitor is a different story. Depends entirely on the interface card and the monitor itself. Chances are, however, that 50' will be a mite too long to go without significant signal loss. At lot of this is dependent on exactly what equipment you have and the quality of its components. I've met serial cards that couldn't drive a signal 30 feet, and parallel cards that blew the tractor feed pins off the printer at 50 feet. All I can suggest is that you try it and see if it works. I wouldn't worry about messing up your keyboard, but exercise some caution with the monitor. Unkydave unkydave@shumv1.ncsu.edu bank@cslimg.ncsu.edu to do with they keyboard - assuming "normal"-
mrichey@orion.oac.uci.edu (Mike Richey) (10/20/89)
In article <4241@ncsuvx.ncsu.edu> unkydave@shumv1.ncsu.edu (David Bank) writes: >In article <[253d2160:289]comp.sys.ibm.pc@nstar.UUCP> akcs.larry@nstar.UUCP (Larry Snyder) writes: >>What is the longest one could build a keyboard/monitor >>extension cable for a VGA or EGA monitor and have it work >>without damaging any of the equipment? >> >>Could it be 40 feet long? 50 feet? > Well, the keyboard is essentially a serial device. A "typical" >serial port (let me know when you find one) can drive about 100 >feet without any noticeable loss of signal. However, the logic operates at 5volts only. It's TTL. 5Volts is supplied directly to the keyboard through the DIN connector, from the system board. IMHO, 30 feet would be pushing it. The Clock and keyboard data operate with standard TTL levels. Michael S. Richey Internet: mrichey@orion.oac.uci.edu Bitnet: MRichey@UCI CompuServe: 71650,3132 Voice: (714) 856-8374 University of California, Irvine Network and Telecommunications Services 342 Computer Science Irvine, CA 92717
toma@tekgvs.LABS.TEK.COM (Tom Almy) (10/20/89)
In article <4241@ncsuvx.ncsu.edu> unkydave@shumv1.ncsu.edu (David Bank) writes: >In article <[253d2160:289]comp.sys.ibm.pc@nstar.UUCP> akcs.larry@nstar.UUCP (Larry Snyder) writes: >>What is the longest one could build a keyboard/monitor >>extension cable for a VGA or EGA monitor and have it work >>without damaging any of the equipment? >>Could it be 40 feet long? 50 feet? > That still doesn't answer your question, does it?? Depending >on how well built the PC is, and what quality of components went >into it, I'd say you have about an 80% chance of doing what you want >with the keyboard [...] >the keyboard is not a concern here. > Now, the monitor is a different story. Depends entirely on the >interface card and the monitor itself. Chances are, however, that >50' will be a mite too long to go without significant signal >loss. Well I beg to disagree on several points. In both the case of the keyboard and an EGA display, all signals are digital, and the distance you can drive (with a given type of cable) is dependent on the driver current (yes, the keyboard matters), the hysteresis of the receiver (noise immunity), and impedence matching. "Quality" is not really the consideration; the shabbiest display card might do the best because they used a cheap driver that just happened to have greater drive capability at the cost of bandwidth (clarity). The cable used will make a major difference. The longer the cable the more you have to worry about crosstalk, shielding (the cable becomes a dandy radio antenna), and capacitive loss. Just connecting up a bunch of keyboard and display extension cords won't hack it -- you'll suffer one or more of these problems. A VGA display makes the situation worse since the analog video levels have little noise immunity and any impedence mismatching will certainly lead to ghost images. I have no idea how far you can really go, but I can tell you that it will be *expensive*, requiring custom cabling. It might be cheaper, if you application can support it, to use a remote terminal on an RS-232 port. This will have no trouble going 50'. Tom Almy toma@tekgvs.labs.tek.com Standard Disclaimers Apply