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Vintage Computers Any vintage computer systems, calculators, video games etc., but with an emphasis on 1980s and earlier equipment.

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Old 18th Jun 2020, 7:42 pm   #1
__i4cy__
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Default GR Electronics Pocket Terminal (circa 1977)

I have cleaned and restored this pocket terminal made by G.R Electronics Ltd, of Newport Gwent.

It seems to use 4-20mA current loop serial interface. Before I power it up and perform some basic testing, does anyone have a user manual for this device?

Thanks.
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Old 18th Jun 2020, 7:50 pm   #2
JohnBHanson
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Looks like an oyster terminal - the ones a know were RS232 - what connector does it have on it?
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Old 18th Jun 2020, 8:51 pm   #3
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Thanks for replying.

Quote:
Originally Posted by JohnBHanson View Post
Looks like an oyster terminal - the ones a know were RS232 - what connector does it have on it?
I don't think this is made by Oyster Terminals, unless they were originally incorporated as G.R Electronics Ltd.

This unit has a 7-pin din plug on the end of the trailing lead. It uses opto-isolators for buffering which is why I am assuming it uses a 4-20mA current loop, and so will not be compatible with RS-232 voltage levels.

I have already worked out the pin-out.

Pocket Term ---- Function
1 - pink RD
2 - white RD-GND
3 - blue n/c
4 - grey GND
5 - brown +5V
6 - green TD
7 - yellow TD-GND

A manual would be useful for understanding how to operate it, and if it offers any special functions, etc.
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Old 18th Jun 2020, 8:56 pm   #4
McMurdo
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Default Re: GR Electronics Pocket Terminal (circa 1977)

They're on Graces Guide;

PS GR Electronics were indeed the original maker of Oyster terminals
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Last edited by McMurdo; 18th Jun 2020 at 9:00 pm. Reason: added the oyster bit
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Old 18th Jun 2020, 9:07 pm   #5
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Quote:
Originally Posted by McMurdo View Post
PS GR Electronics were indeed the original maker of Oyster terminals
Oyster Terminals UK Ltd seem to be no longer trading either.

Did they publish any of their manuals online?
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Old 18th Jun 2020, 9:16 pm   #6
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Looks vary much like a TI58 calculator to me.
 
Old 18th Jun 2020, 9:18 pm   #7
McMurdo
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Default Re: GR Electronics Pocket Terminal (circa 1977)

I'm not sure. Oyster have been through several changes of ownership through the years like many computer companies. The last time I tried to order parts (back end of last year) I found they had gone out of business again a few weeks earlier. Here's an old magazine advert for yours;
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Old 18th Jun 2020, 9:23 pm   #8
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Quote:
Originally Posted by McMurdo View Post
Here's an old magazine advert for yours;
I've already seen this ETI July 1978 press article, the terminal was also mentioned in Elektor January 1979.

Thanks anyway.
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Old 18th Jun 2020, 9:26 pm   #9
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Default Re: GR Electronics Pocket Terminal (circa 1977)

Quote:
Looks vary much like a TI58 calculator to me
there's one on ebay with a bubble-led display at the top which looks otherwise like the OP's version.
GR Electronics originally made a portable terminal that opened up like a clamshell, I think this is where the name Oyster came from.

http://www.computinghistory.org.uk/d...-165-computer/
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Old 21st Jun 2020, 11:09 pm   #10
__i4cy__
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Default Re: GR Electronics Pocket Terminal (circa 1977)

I worked it all out in the end without any manual.

The Pocket Terminal is now restored and repaired having had to change the 4N25 opto-isolator. It is shown here connected in "loopback" so I am able to echo entered characters to the display.
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