info-terms (04/02/83)
>From UCBVAX.@MIT-MC.alpines@G.CC Sat Apr 2 04:54:08 1983
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I've recently acquired a Tandberg Data model TDV2220 display terminal.
Here are my comments for anyone interested.
Capabilities: The terminal has virtually every editing feature one
could ask for, including, but not limited to,
add/delete line
add/delete character
erase fields: to beginning, to end and all
erase lines: to beginning, to end and all
The add/delete operations are on the slow side --
most everything is done in firmware. The terminal has
several forms of protected fields.
Display attributes include underline, reverse video,
blinking, reduced intensity and various combinations
thereof. There are no `magic cookies' left.
All control sequences follow the ECMA-48 standards,
equivalent to ANSI X3.64. The terminal will operate
in either 8-bit (plus parity, if desired) or 7-bit
(again, plus optional parity) modes. In 8-bit mode,
the 8-bit ECMA sequences are used, although it will
accept the 7-bit equivalents. When in 8-bit mode,
any editing keys pressed at the terminal will send
the 8-bit codes (if the terminal is set in a `duplex'
editing mode -- one of several modes available).
The terminal has four character sets, the main
ASCII/ECMA set, a set of very complete (96) line
drawing and histogramming characters, a set of
superscript/subscript characters, and a set of
characters for displaying control codes as two
tiny letters (these are printed only when in a
`monitor' mode which prints control codes rather
than executing them -- very handy for debugging
`termcap' descriptions).
Ergonomics: My primary reason for buying the terminal. It has
a very large (15 inch diagonal) screen which is
backlit. It has green phosphors, so the text is
light green, superimposed on a darker green
background. Unlike the `reverse video' mode on many
terminals, the green background is much lighter and
is consistent across the entire screen -- there is
no border. I have found the screen to be VERY nice,
far better than anything else I have ever used.
The letters are formed in a very dense dot matrix
on 25 lines. Eye strain is probably as minimal as
can be.
The monitor sits atop a stand which allows one to
adjust the monitor in every direction: tilt, swivel
and height. The detached keyboard is expansive and
has a very low profile. The home row keys are
barely an inch above the tabletop. The keys are
interesting: they are not like most `typewriter'
style keyboards. The keys have a slightly oval
top which is molded onto a square or rectangular
matrix of abutting bases. The oval tops are sculpted
with a shallow indentation. The keys give resistance
which increases up to a point, when they register, then
resistance drops until you hit the floor. The touch
is very light. It takes a little time to get used to
the keyboard, but one becomes addicted to it on short
order. What takes getting used to is first the physical
design of the keys and second the placement of some
common keys: CR, Control, Tab and Escape. The CR key
is at the far right and is a vertical key extending for
two normal keylengths, but with no horizontal extension
at the top. The linefeed is just above it, slightly
elongated horizontally. The tab is above the left-hand
shift key and is the same size as any alphabetic key.
The control is right next to `Q' and again is small.
The escape key is to the immediate left of the control
key, again small. The backspace key is above the
linefeed key on the right. The delete key is on the
row of programmable function keys (8 of them, plus
shifted versions, making 16), to the far left, at
two key rows above the numeric keys. This could be
bad news for DEC people.
In addition to the function keys, it has a complete
set of arrow keys, a numeric keypad and a number of
editing keys. You can control DTR from the keyboard.
Flexibility: The terminal's operating characteristics are changed
in firmware through a set of six full-screen menus.
The menus are a wholesale improvement on the VT100
style menus. They contain a full descriptive text
of each feature and the options for each feature
are mnemonics. One uses the arrow keys to go up
and down each menu, pressing <return> shows the options
for each feature and the left/right arrow keys select
the desired option. Pressing <return> goes back to
the full menu. Tabs can be set through the menus,
as can the function keys. All the settings are remembered
in EAROM.
The terminal has two input ports supplied standard,
one RS-422, the other RS-232. An additional port
is available. It has a printer port with RS-422
standard, RS-232 as an option, with 2k buffer.
Various printing modes are available, including
transparent printing from the input channels and
selective printing of fields from the screen
buffer, which may be up to 8 pages in length,
contiguous or divided into screenfuls.
Disabilities: When using emacs, the fact that the control keys
do not repeat (the other keys do) can be annoying.
The slowness of the delete/add line/character
operations is a small damper on editing. With
emacs, I've had problems with lost text from
buffer overflows when emacs was busy adding
lines and then sending the text afterwards.
I'm using James Gosling's emacs, which does not
support the XON/XOFF protocol the terminal uses
to avoid input buffer overflow.
If you are using the editing keys in the mode where
they transmit their codes without doing anything,
there is no escape to use the keys locally, without
changing the terminal mode. It's not a big deal,
however, to change the mode. Nonetheless, it spurred
me to write a program to `mirror' control codes so
that I could scroll up and down through pages of
memory. A side effect of this is that one can return
the terminal to local mode to use the keys by taking
the terminal off-line. The off-line key, however,
drops DTR, which will cause some modems to go off
line. On the other hand, being able to drop DTR
with a stroke of a key is very handy with an auto-dial
modem sitting across a room.
Using `vi' with this terminal will cause `ripples'
on the screen when upscrolling, since `vi' insists
on using the `al' capability to upscroll, regardless
of whether `sr' is defined.
Smooth scroll on the terminal doesn't work properly.
Apparently it takes a lot of overhead and the
display processor can generate `flashes' on the screen
depending on what's being scrolled. I found these
flashes annoying enough that I don't use smooth scroll
anymore when in multipage mode.
For home use, be warned that the terminal has a very
heavy inrush current -- the specs say up to 20 amps.
Once operating, it takes only 50 watts. On the plus
side, however, it is very well shielded and I have
had no interference from it at all. It is also well
protected against power transients and noise.
The terminal checks parity, if you specify a parity
bit. A little error LED lights up on the front panel,
though the proper character will appear on the screen
(not a block as on some terminals which check parity).
This can be a bit annoying with Unix, where parity is
not something which is handled well or consistently.
Also, if one is in 8-bit mode, strange characters
appear, since the terminal has a 256-character set.
Price: Basic terminal is $1875. 8 pages of memory cost
an additional $150. Manual is $40 (very complete).
Service manual is $100. Additional input port is
$40. RS-232C printer port is $40, 2k print buffer
is $10.
Miscellaneous: The terminal is also available with a VT100 emulator.
For those who purchase this terminal, I have a
`termcap' entry for it.
Summary: I'm on the whole very happy with the terminal. I bought
it for ergonomics and I've been more than satisfied
in that category. I was a bit disappointed that the
smooth scroll didn't work properly and that the
add/delete operations were so slow. It's a very
attractive terminal, and for home use that, together
with its lack of interference, is very appealing.
I really like the set-up menus, too.
Harry Weeks
Bytel Corporation
Berkeley, California
(415) 527-1157