macmillan%wnre.aecl.cdn%ubc.CSNET@CSNET-RELAY.ARPA.UUCP (05/17/86)
We have a Tektronix 4100 series terminal connected to a uVAX DHV-11 line operating at 9.6 Kb/s. The machines are 250 feet apart. Can a faster connection be made? (the terminal supports 38.4 Kb/s) It is not practical to move the terminal closer to the uVAX. An existing Ethernet cable could be extended and a connection made through a DECserver100. That would give 19.2 Kb/s. Better, but expensive. John MacMillan Atomic Energy of Canada Whiteshell Nuclear Research Establishment Pinawa, MB, Canada R0E 1L0 (204) 753-2311 ext. 2539
jbs@EDDIE.MIT.EDU.UUCP (05/21/86)
In article <162:macmillan@wnre.aecl.cdn> macmillan%wnre.aecl.cdn@UBC.CSNET (John MacMillan) writes: >We have a Tektronix 4100 series terminal connected to a uVAX DHV-11 line >operating at 9.6 Kb/s. The machines are 250 feet apart. Can a faster >connection be made? (the terminal supports 38.4 Kb/s) The DHV-11 supports 38.4K Baud, I believe, and I know it supports 19.2K Baud, since I use it. As for whether or not the length of the terminal line is a problem, the only answer I know is to try it. If it works, fine. I've had 1000 foot lines work at 9600 baud, after being told it woudn't. You might also consider some sort of line-driver, which extends the range of RS-232 communcations. Black Box people, for example, make these. Jeff Siegal
cetron%utah-cbd@UTAH-CS.ARPA (Ed Cetron) (05/22/86)
I have one terminal line from a DH11 on my 11/44 which is running 19.2k for over 700 feet....I get a 1% error rate...the best suggestion is to try it, 250 feet is not all that long...a special low-loss, low-capacitance cable will also help.... -ed cetron cetron%utah-cbd@utah-cs.arpa
bzs@CSNET-RELAY.ARPA.UUCP (05/25/86)
>From: jbs@MIT-EDDIE.ARPA (Jeff Siegal) >As for whether or not the length of the >terminal line is a problem, the only answer I know is to try it. If >it works, fine. I've had 1000 foot lines work at 9600 baud, after >being told it woudn't. I remember hearing a rumor once that there is a reason DEC's muxes usually work past the "official" RS232 length limits, like that they were designed to. Anyone know anymore? (of course, this may depend on the mux.) Might help settle this periennial argument between the spec's folks and the "but I've done it a thousand times" folks (like me.) -Barry Shein, Boston University
Magill@upenn.CSNET (CETS Operations Manager) (05/28/86)
The EIA RS232 length limit of 50 feet was created around a certain wide standard of voltage levels and corresponding line losses and load factors. The EIA signal may be from + or - 3 to + or - 25 volts with the specification that when properly loaded (3000-7000 ohms) the signal at the "interface point" shall be not less than 5 volts nor more thatn 15 volts in magnitude. Therefore sufice it to say that if you: a) increase receiver sensitivity (being able to "read" a low incoming voltage level (+- 3) while not being killed by a high level (+-15), b) increase your output transmitter so that you stay closer to the +- 15 volt signal level than to the +- 5 level c) use low loss transmission cable d) use shielded transmission cable Use of any or all of the above techniques will markedly change the distances available to you for an EIA RS232 connection. You will discover that terminal "A" will work reliably at high speed (9600 -19.2k) for 300 feet, but that terminal "B" will only work reliably at a maximum speed of 2400 baud at 300 feet, and that terminal "C" won't even work beyond 100 feet. Today, all of the above is changing as the Communications world evolves from the "unbalanced" world of EIA RS232 into the "unbalanced/balanced" world of EIA RS443 into the "balanced" world of EIA RS449. You will note that on page 4 of your latest DECDirect catalog update that DEC423 appears. One of the major goals of the new standards is the achievement of higher transmission speeds over longer distances, reliably.