Neat item! If you can't turn up any docs..
here's a thought.
Since you'd only need one switch to toggle 110 / 300, that potentially
leaves five for other uses. Not to say they only used one switch for that
setting, maybe their design required two.. but only one is +required+ at a
minimum.
Pretty safe to say that additional switches are used to manually assert /
de-assert various hardware flow control and device / ring detection lines
(CTS, DSR, DCD / RLSD) and/or enable / disable hardware flow control. You
should be able to test for the manual line settings by watching the
appropriate pins with a meter while trying different switches - see which
lines are being pulled high / low.
So how the heck do you operate a one-line terminal, anyway? Does it have a
scroll-back buffer of 5-10 lines? Do you just have to read way, way fast?
;-)
On Sun, Apr 26, 2015 at 9:06 AM, E. Groenenberg <quapla at xs4all.nl> wrote:
Sifting through a box of odds 'n ends I came across a sort of pocket
terminal. It's casing is of the earlier models TI wedge calculators
and has an 8 digit display. Internally there is an intel 8048 processor
with some support ttl ic's.
A spiral cable with a Db25 connectors goes out from where normally the
charger port would have been for the calculators.
Behind the battery cover (no space for a battery tough) is a dip switch
block with 6 switches.
It's made by 'G.R. Electronics LTD' wich had 2 addresses,
one in the UK and one in the USA.
Google did came with an advert of this device ($395 in 1979) and
mentions
a selectable speed of 110 - 300 baud and requires a 5V at 450mA.
I was wondering if a list member could tell me what the switches are
supposed to do (besides setting the speed)
Funny enough, a similar unit was sold recently (item no 220662386232)
which
has a way higher serial (mine has 7786R)
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Hmm, only 7 wires are connected, and in the connector 2 wires are
joined at one pin, and the blue wire is not used in the db25 connector
housing, so only 5 wires are effectively used.
The wiring :
PockTerm ---- DB25
1 - pink pin 3
2 - white pin 4,20
3 - blue nc
4 - grey pin 7
5 - brown pin 9
6 - green pin 2
7 - yellow pin 7
Pin 9 is somewhat unusual, maybe for power?
Regarding the switches, one for 110/300, one (or 2) for parity control
and one for number of stop bits? Left over are 3 or 2 other settings.
Ed
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