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TL;DR: It's a classic case of technological advancement vs. installed base In the early days of electricity-based communication (i.e., telegraph and later TTY) there was no way to detect a voltage and, when needed, amplify it. Only current flowing in a closed circuit could be detected reliably—by having it run through a coil which in turn moved a lever—and ...


The current loop goes all the way back to classic telegraphy. If there's current flowing, then that's one state. If there's no current, then that's another state. It's as simple as it can be. You don't need to manipulate voltages. That's the key. Just turn a literal switch on and off. It also has problems. Current losses are heavy even in short ...


The advantage of RS-232 was that it was a formal standard that defined the electrical interface between equipment, down to handshake signal usage, voltage levels and connector pinout. Even though devices only implemented a relevant subset of the standard, and the implementations did vary and were sometimes not directly compatible, in general, only a simple ...


This post appears to contain original .ASM source code for a VT52.SYS (but it may not be the same VT52.SYS you've seen references to). You would need an assembler (like MASM) to assemble it:


Current loops are better for signal integrity for long runs because they are generally only "grounded" to a fixed potential at the current source. This means that there's no "ground loop" for stray magnetic fields to interact with. For electromechanical devices this is easy to implement: switches and relays don't need a common "...


a company like DEC that made both the computers and the terminals Actually a lot of DEC computers (PDP-8, PDP-11) had teletypes as I/O devices. Teletypes used 20ma current loops so DEC needed to provide such. Only later did DECWriters and the VT series of CRTs become the usual I/O.


The VT52 terminal escape codes should work fine within VT100 or VT220 Emulation. Later generations are able to support earlier codes. VT240 is the first terminal to support color displays as color for instance. This is VT color not ANSI. You should be able to run something like Putty on a windows computer and then attach to your device over the serial port. ...


I found a copy at, inside an OS/2 development boot floppy:


Downloading VT52.SYS from a virtual machine on requires a few steps that may not be obvious if you're unfamiliar with the website: Go to a PCjs virtual machine (like the one that @john_e already posted) Make sure the desired disk, "OS/2 FOOTBALL (v7.68.17)", is loaded in drive A: Click the Save button Click OK on the "Check your Downloads folder ...


It seems that this is a mistake from the terminfo entry (it wouldn't be the first). The only difference between the VT50 and VT50H is the keypad, not the command set, and another document from DEC: VT50 user's manual (issued in 1975), clearly indicates, consistently with the document you mentioned, that "ESC I" has no effect on the VT50 (see page 19). ...


MS-DOS Kermit had a terminal emulator built in. It should be VT100 compatible, and thus VT52 backward compatible. I don't know if Kermit was based on a driver or whether terminal emulation was part of the app. You might be able to download MS-DOS Kermit and check it out.

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