A customer has a MAINFRAME running RS232 ports
Once a week he takes a Screen & Printer 300m to another building, connecting back to the mainframe using a Multiplexer & Line DRIVERS, he's now experiencing problems with this conection THOUGH everything works fine when at the host end
Since RS232 is outdated & spares are becoming harder to FIND what advice would you suggest I give to the customer regarding replacing his current setup

Thanks for all adviceCan you tunnel the connection over a LAN? 300m is going to be a problem for many cabling standards , with the possible exception of optical. Routing via TCP/IP gives much better long-distance possibilities, but I'm not sure your hardware application can be routed in that way. What exactly does the computer need to do REMOTELY?The User has no PCs but "Dumb" Terminals that have no Ethernet connection just RS232 or RS422
I know its all antiquated but some people are not for change.

THe terminal connects through the Line Drivers at the remote end to the Host Mainframe so the Terminal Inputs data to the mainframe as though it was connected directly

My suspicion is the Line Drivers or Multiplexers have failed, I will know more after a site visit on MondayEek. I thought that might be the case. I haven't seen that kind of kit since I was at university. You could consider selling this user the notion that supporting such systems is far more expensive than supporting newer kit...