On Mon, 29 Dec 2003, Witchy wrote: Thinwire/thickwire = does this equal x-length of good 50 ohm coax with BNCs on either end? If so - thats covered. What I'm *not* doing is terminating - I didn't figure I'd have to with each connector on the servers joined by a single run of coax. I have the BNC Ts - should each end also need 50 Ohms...? Mongo not Grok LAN voodoo... 2 50 Ohm terms per port? Mongo very confused now... Mongo Least Significant Bit in Error Register of Life.... Cheers John

Yes, you need to terminate. Otherwise you get all sorts of signal reflections when the impedance changes at the end of the coax, and the error rate goes through the ceiling in consequence. I don't really _understand_ transmission-line effects. But I know they exist and I know that you don't play fast and loose with them unless you know _exactly_ what you're doing (or you don't care about whether it works or not). Only if the port is not connected to anyone else. Two 50-ohm terminators per thinwire segment. A box on its own is just a very very small thinwire segment...and it wants those two terminators. (Instead of a T with two 50-ohm terminators, you probably could get by with a single 25-ohm "terminator" directly on the connector, since all the distances are very much less than the carrier wavelength. But that would mean finding such a thing.) /~\ The ASCII der Mouse \ / Ribbon Campaign X Against HTML mouse(a)rodents.montreal.qc.ca / \ Email! 7D C8 61 52 5D E7 2D 39 4E F1 31 3E E8 B3 27 4B

50. 75 is for video isn't it? I might have a dead tree edition somewhere if you get desperate. cheers -- adrian/witchy www.binarydinosaurs.co.uk - the online computer museum www.snakebiteandblack.co.uk - ex-monthly gothic shenanigans :o(

At a pinch, in place of fancy terminators, I've used 47R resistors, one end poked into the center hole in the side of a T piece, the other end firmly taped to the shell. They worked, probably not perfectly, but well enough to prove a point to someone. I've got a terminal server in a box somewhere ... rescued from a customer site we took over some years ago. 16 port, and a decent and expensive make I found at the time. It had about three serial printers attached to it, and was being used as a print server... terrible waste.. I've got plans to use it to resurrect my BBC Micro based BBS and put it on the internet... one day perhaps I'll have the space to set it up again. BTW ... Anybody in the north-west UK need a technician with lots of experience across the board? My Christmas present from my boss this year was to not have a job to come back to.

That should be OK for the cable. YES. You _must_ terminate both ends of the thinwire segment, no matter how short it is. This is due to the design of the ethernet transceiver, the transmit part of which is a current source that develops a voltage across the terminator resistors. If you don't terminate properly, then the votlage on the network cable goes too high, which is exactly how a colision is detected... Fit the T-pieces and 50 Ohm terminetors (a BNC plug with a 50 ohm -- or 51 ohm -- resistor between pin and case) at each end and try again. If you have nothing connected to the thinwire port (no network cable), then you need to provide a 25 ohm resistance (i.e. 2 50 ohms in parallel -- the DC condition of a terminated thinwire cable) between the centre and sheild of the thinwire connector. Otherwise the darn thing fails the selftest (IIRC) for much the same reason as above. -tony

That'll be the 90TL then :) witchy

LAT is the protocol used by most DECservers. Based on what Witchy said, I think you can do what you want, *IF* you have a 90TL hooked up to the ports on the /44. You'll also need a terminal hooked up at least temporarily to setup the ports on the 90TL. (One of these days I really need to break down and get myself a 90TL). Also, as someone pointed out you need the 10Base2 segment to have a pair of 50-ohm terminators. Like this: Terminator --- T-joint --- Wire ---T-joint --- Terminator | | DECserver #1 DECserver #2 Also, if you have a 10BaseT or 100BaseT connection between the office and the /44, you can use either a 10BaseT-to-10Base2 converters or a pair of 10BaseT hubs with 10Base2 connectors (these make good cheap converters) to keep from having to run the 10Base2 wire between the two locations. Don't blame you, I've been pondering trying to make my 90L+ wireless, though I'm not sure it would be worth the effort in my case (finding three receptacles would be harder than stringing a wire). I want to be able to kick back on the sofa with a VT420 :^) Zane -- -- | Zane H. Healy | UNIX Systems Administrator | | healyzh(a)aracnet.com (primary) | OpenVMS Enthusiast | | | Classic Computer Collector | +----------------------------------+----------------------------+ | Empire of the Petal Throne and Traveller Role Playing, | | PDP-10 Emulation and Zane's Computer Museum. | | http://www.aracnet.com/~healyzh/ |

On Mon, 29 Dec 2003, Witchy wrote: Ah. Rats!! So I cannot hook terminals X1, X2, Xn to one 90L+; thence via (properly terminated) RG /58 50 ohm coax to the second 90L+ with the corresponding serial ports hooked to Machine Ports Y1, Y2, Yn... What I understand now is that the 90L+ is "single-ended" device that expects some server-thingy / software on the other end of the Thinwire...? Well - saved me a cold slog into Carson City tomorrow... ;{} Anyone wanna trade these things for a multi-port (8 is too many) RS232 - LAN - RS232 pair of multiplexers / terminal servers / apparatus? Cheers John

Nope. You need a minimum of a 90TL do to that. 90L+'s were brilliant for small companies that needed terminal access out of the box with pretty much no configuration other than maybe setting up a port to be a printer port and the baud rates. LAT. It's a very small footprint server service that presents the machines its running on as connectable resources with ratings based on how loaded a particular machine is. It only does terminal access and printers and wasn't really designed for large networks, though we did manage it on occasion :) Remote disk access that was available through the Infoserver was done using the LAD/LAST protocol, which was also how the original versions of Pathworks (PCSA?) worked before they moved onto the SMB protocol. Aah, happy days with PCSA. Not. cheers w

LAT is not DECnet. You can have DECnet without LAT and LAT without DECnet. -- Eric Dittman dittman(a)dittman.net

On Sun, 28 Dec 2003, Paul Thompson wrote: Both RS232 ports are connected via the appropriate adapters tp Ports 1 on the 90s. there is nothing unless I hit 'return' on the VT220 - then the previously reported error message is generated, once per press. Thanks - John