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by vjshah
261 days ago
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I used to work at a DoorDash-type company in the early 2000s. Back then, we passed the orders onto the restaurant by faxing them. We had a machine with I believe 16 modems (might have been 20?) attached to do the faxing. I would have loved to try something like this with that setup. |
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From the instrument company they had a 4-channel RS-232 "Autoswitch" you could wire into the serial port from 4 instruments, then the fifth cable ran to a dumb terminal CRT console, and you could access any one of the instruments by sending unique control codes to switch communication channels.
Those Autoswitches were about a $1000 option. Instead, most people who were doing something like this used a manual switch from Radio Shack that was about 50 bucks.
Alternatively, you could unplug the local CRT terminal and connect the serial cable to a phone modem instead. Your instruments then had a telephone number.
You could then call from anywhere to access the data and control the instruments. As long as you had a modem and terminal at any remote location. Long-distance charges may apply :)
Using 1980's design equipment.
In 2001 the Sony smartphone made it possible to remotely call in on a cellular, link it to your laptop by infrared, and use Hyperterminal in Windows XP instead of a local CRT if you wanted to also. They had this to an extent before XP, Bluetooth, and USB anyway.
But with a manual switch you couldn't switch instruments remotely 24/7 unless there was somebody on site 24/7, not without an autoswitch.
At Exxon, 4 channels was not enough, and there were AT&T rack units like this, way more powerful, with built-in modems for direct connection to the phone lines.
Never did use the rack one I got since all my instruments were in the same lab at the time, and before I could make a move, ethernet became dominant which joined each instrument's PC quite well when it was built into Windows, instead of having to join instruments together in some way beforehand.
All I had to do so I could have a PC for each of the old RS-232 instruments was to "just" write my own code to accomplish both, "concurrently" for instruments never designed for DOS interfacing, much less Windows.