[Info-vax] SET TERM /TTSYNC on ancient VMS versions

[Chris]

On 08/16/18 16:52, Johnny Billquist wrote:

>
> Not entirely true. DEC terminals always had support for DTR/DSR. But
> that is used to indicate if something is connected or not, and is not
> used for flow control. The DTR/DSR is also included in the MMJ.
> All DEC terminals have flow control using XON/XOFF. I'm trying to
> remember if maybe VT05 might be an exception, but I think not. But all
> terminals after the VT05 definitely have XON/XOFF flow control.

Using RT11 in the late eighties, control s , control q worked for
scrolling, but pretty sure the vt220 could be setup from full
modem control or xon / xoff. Of course, all terminals have the manual
function from the keyboard. Full modem control would be needed for even
the earliest dec acoustic coupler modems and dec had handbooks in the
late 70/'s covering that sort of comms. Iirc, some dec terminals even
supported current loop, to connect to asr33 teletype interfaces, but
that was eons ago :-).

>
> Speaking of modem control, DEC terminals actually supported as much of
> the modem control signalling that can be said to have been useful, and
> that was way more than just 3 wires. It's just that people today seem to
> be blissfully unaware of what modem control was meant for.
>

I ran an anonymous vax mail login on a uvax II years ago for a local
group, before I had full isp access and that used all the modem control
lines. Lots of fun setting that up, but had the grey wall back then.
Fwir, that was VMS 5.4 era. Depends on the interface though,as some of
the dec serial interfaces were 3 wire only, or current loop


> No. Modem control, as related to modems, were not about flow control,
> but about handling half duplex communication. And that does indeed go
> back decades, since noone have probably seen half duplex in the last 30
> years. :-)
<
> In rather recent times, the modem control signalling was redefined in an
> RS-232 revision to instead be used for flow control, which had started
> to become the industry standard anyway. But DECs use comes from before
> that, and is based on what the standard actually said at the time.

As implied, dec wrote the book on a lot of the early comms stuff...

Chris