steve@wattres.UUCP (Steve Watt) (02/15/90)
I was trying to get a Ventel Pathfinder 18K up on a DecStation 3100 running UWS 2.1, and having absolutely no success. The Ventel looks like a Telebit T1000, mostly. My problem: If I set up the /etc/remote file so it has some 19200 baud entries, add it to my L-devices, and then try to cu to it, cu (which dumps core if not invoked exactly right) says "Connected", and then typing "A<pause>A<pause>AT<enter>" does not get me an OK. It does work when attached to a PC. I hooked in the breakout box, and did not see any notable differences in the signals going into the modem. Dropping the speed doesn't do anything, until you get down to 2400 baud. Then it works OK. Ugh. Any suggestions out there?? -- Steve Watt ...!claris!wattres!steve wattres!steve@claris.com is reported to work. Is rm -rf a way to remove high-frequency noise? (No names mentioned! :-)
steve@wattres.UUCP (Steve Watt) (02/17/90)
In article <422@wattres.UUCP> I wrote: >I was trying to get a Ventel Pathfinder 18K up on a DecStation 3100 running I have discovered why this doesn't work: If you hang an oscilloscope off of the serial port on the DECStation 3100, you see a voltage swing of -5v to +5v !!! I realize that this is "officially" allowed in RS232-C, (but not -D), but the "usually accepted" value is somewhere around +-12v. The VAXStation 3100, incidentally, swings +-10v, which works OK. My portable swings +-8v, which also works. Does anybody know if there is some way to coax more voltage swing out of these things, or do I get to do some electronic design? (Like buying from SGI? :) -- Steve Watt ...!claris!wattres!steve wattres!steve@claris.com is reported to work. Is rm -rf a way to remove high-frequency noise? (No names mentioned! :-)
hans@umd5.umd.edu (Hans Breitenlohner) (02/20/90)
In article <423@wattres.UUCP> steve@wattres.UUCP (Steve Watt) writes: >I have discovered why this doesn't work: If you hang an oscilloscope off of >the serial port on the DECStation 3100, you see a voltage swing of -5v to +5v >!!! I realize that this is "officially" allowed in RS232-C, (but not -D), but And what does RS232-D specify for voltage levels? Personally, I would consider anything that can not operate on +/- 5 Volts broken. (I assume that is under load, not open circuited). The only time we have run into anything like that was with line drivers which were powered from one of the control signals (DTR?), which failed mysteriously when that signal was too low (though within RS232-C specs). I would be surprised if your modem was powered from the interface, but if it is, it may be fairly easy to substitute a highere voltage on the appropriate line.
steve@wattres.UUCP (Steve Watt) (02/21/90)
In article <6152@umd5.umd.edu> hans@umd5.umd.edu (Hans Breitenlohner) writes: >In article <423@wattres.UUCP> steve@wattres.UUCP (Steve Watt) writes: >>I have discovered why this doesn't work: If you hang an oscilloscope off of >>the serial port on the DECStation 3100, you see a voltage swing of -5v to +5v >Personally, I would consider anything that can not operate on +/- 5 Volts >broken. (I assume that is under load, not open circuited). The +-5 was unloaded. Loaded, it dropped to about 4.8v, definitely below the threshhold. Since +-5 is exactly at the edge of the acceptable band, I don't think that it is broken. The intent of the band is for the voltage drop that occurs on longer wires. >I would be surprised if your modem was powered from the interface, but >if it is, it may be fairly easy to substitute a highere voltage on the >appropriate line. The modem (a VenTel Pathfinder 18K) is definitely NOT powered from the RS232 line. It comes with a rather large transformer. Just curious: Does anybody know of an "RS232 signal booster" of some sort? Like where to buy one, or schematics or something? -- Steve Watt ...!ames!claris!wattres!steve wattres!steve@claris.com also works Is rm -rf a way to remove high-frequency noise? (No names mentioned! :)
grr@cbmvax.commodore.com (George Robbins) (02/21/90)
In article <432@wattres.UUCP> steve@wattres.UUCP (Steve Watt) writes: > In article <6152@umd5.umd.edu> hans@umd5.umd.edu (Hans Breitenlohner) writes: > >In article <423@wattres.UUCP> steve@wattres.UUCP (Steve Watt) writes: > >>I have discovered why this doesn't work: If you hang an oscilloscope off of > >>the serial port on the DECStation 3100, you see a voltage swing of -5v to +5v > > >Personally, I would consider anything that can not operate on +/- 5 Volts > >broken. (I assume that is under load, not open circuited). > > Just curious: Does anybody know of an "RS232 signal booster" of some sort? > Like where to buy one, or schematics or something? Yes, you can get "RS232 Line Extenders" that are probably just an RS232 receiver and driver with a power supply. Black Box and others have them, but you'd want to be sure they handle modem control and not just transmit/ receive signals. You can do the same with some 1488's and 1489's from Radio Shack... Note that the threshold voltage for 1489's can be controlled by a resitor between the "response control" pin and one of the power supply rails. I'd halfway suspect the modem is doing something like this to shift the threshold to prevent no-connect "chatter", otherwise the threshold should be only a volt or so... -- George Robbins - now working for, uucp: {uunet|pyramid|rutgers}!cbmvax!grr but no way officially representing: domain: grr@cbmvax.commodore.com Commodore, Engineering Department phone: 215-431-9349 (only by moonlite)