Hi, We have remote access to our system, via a modem & multiplexor combo. Basically, the remote site has VT terminals and line printers accessing our system through a multiplexor and modem, which dials into our modem and through our mulitplexor, then into a DEC terminal server. The remote site would like to add another terminal on there end. However, I am not sure the max line length of the serial cable running from the terminal to the multiplexor/modem on their end. The distance to the new terminal would be approx. 200 feet. Can the serial cable/multiplexor set-up handle this length? All the current devices they run, are within 20 feet of their multiplexor. Any info would be appreciated! Thanks, BD.
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Serial Line lengths with Multiplexor
- Thread starter BitDoctor
- Start date
daronwilson
Vendor
Good Question!
Assuming you are talking about RS-232, the recommendation is generally short distances (less than 50 feet) and relatively slow data rates (up to 20 kbps). However, in practice, these limits are commonly exceeded.
The quality of the serial cable, and the quality (i.e. power) of the active components can get you a lot further than 50 feet. I know of no way to tell you how far exactly, but I do have some experience with it.
I have routinely pushed RS-232 via 24 gage telephone wire upwards of 250 feet at 9600 baud or less. I have run dumb terminals upwards of 200 feet on Cat5 cable with no problems at 9600 baud. When I have experienced problems it has been at 19.2k or higher and generally when hardware flow control was implemented.
If you need to go further, you may want to consider a short haul modem. It takes your RS-232 serial in one end, goes 1000 feet or so on two pairs and then converts it back to RS-232. Essentially I think it just converts RS-232 to RS-422/485 and extends the distance.
Your hardware may be robust enough to handle it without a short haul modem if the speed is slow enought.
Reference - Data Communications Explained - QUATECH (equipment manufacturer online)
Good Luck It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
Assuming you are talking about RS-232, the recommendation is generally short distances (less than 50 feet) and relatively slow data rates (up to 20 kbps). However, in practice, these limits are commonly exceeded.
The quality of the serial cable, and the quality (i.e. power) of the active components can get you a lot further than 50 feet. I know of no way to tell you how far exactly, but I do have some experience with it.
I have routinely pushed RS-232 via 24 gage telephone wire upwards of 250 feet at 9600 baud or less. I have run dumb terminals upwards of 200 feet on Cat5 cable with no problems at 9600 baud. When I have experienced problems it has been at 19.2k or higher and generally when hardware flow control was implemented.
If you need to go further, you may want to consider a short haul modem. It takes your RS-232 serial in one end, goes 1000 feet or so on two pairs and then converts it back to RS-232. Essentially I think it just converts RS-232 to RS-422/485 and extends the distance.
Your hardware may be robust enough to handle it without a short haul modem if the speed is slow enought.
Reference - Data Communications Explained - QUATECH (equipment manufacturer online)
Good Luck It is only my opinion, based on my experience and education...I am always willing to learn, educate me!
Daron J. Wilson, RCDD
daron.wilson@lhmorris.com
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