17 Mar
2007
17 Mar
'07
5:32 a.m.
I think the keyboards were made up by putting keyswitches into a metal
plate then wiring them up in row and column form. A ttl system scanned
the rows and columns until it found a closed switch. The count was then
equal to the value of the character.
-----Original Message-----
From: cctech-bounces at classiccmp.org
[mailto:cctech-bounces at classiccmp.org] On Behalf Of Tony Duell
Sent: 16 March 2007 23:22
To: cctalk at classiccmp.org
Subject: Re: old terminals...
Old terminals
In the UK in the early 1970's I worked for a (then small) UK
company
called Newbury Labs.
FWIW, Newbury terminals were common at Cambridge University in the 1980s
(but were being replaced by BBC micros running a terminal emoulator). I
think they were around at other UK universities too.
We made VDU's or video terminals. The early types
used eight bit
parallel shift registers as screen memory.
The model number was 2480 i.e. 24 Rows of 80 Characters. They came in
steel enclosures (painted blue!!) The screen was a 12" tube as used in
mono portable TV's.
When I needed a replacement CRT for a Volker-Craig terminal (it has an
APL cahracter set, which is why I was repairing it), the only way to get
one was to buy a cheap protable TV and remove the CRT from it. Nobody
stocked the CRT on its own.
We used to spend half an hour on each one fixing up
the screen
geometry with small magnets.
The newer ones used a crude stored program system made out of TTL ie
no Microprocessors.
I have a Newbury terminal somwehre. I forget the model, but it's a later
one with a separate keyboard linked up by a wide ribbon cable (I think
the connections are just the row and column lines of a switch matrix,
there's not much, if any, electronics in the keyboard).
I've not been inside it for 20 years, but I thought there was a
microproceossor in there. I do rememeber a board of TTL incluing some
'181 ALUs, though.
-tony