21 Apr
2016
21 Apr
'16
3:22 p.m.
On Thu, 21 Apr 2016, Guy Sotomayor wrote:
3270 terminals are what are termed CUT terminals
(can?t remember what the
acronym means) but were connected to a controller via coax.
Ah okay. Someone told me that the voltage on those was enough to feel/shock
you. Was that true, or just a myth ?
The terminals are ?page mode?. Basically all of the
editing on the screen
is done locally and then when an ?attention? key is pressed the
controller can request the contents of the screen.
Ah, so there was some electrical signaling going on to the terminal
controller and that couldn't be done in sofware, if I'm understanding you
correctly. Hmm, considering all the limitations at the time, it's seems
like that whole 'buffer <-> forward <-> update' mechanism isn't a
bad idea.
With the advent of TCP/IP on the 370/390/zSeries
machines (both HW and SW)
most physical 3270 terminals have gone away to be replaced by TN3270.
Ah, okay and this is where software emulation became an option, I take it.
I had to look up the "TN" part, I didn't find anything solid, but from
some Wikipedia chatter I take it to mean "TelNet". Also guessing they
created some out-of-band channel to send all the stuff that used to rely
on electrical signaling.
Thanks a lot for taking the time to explain that.
-Swift