April 26, 2023
The Entrex Datascope
My primary interest is the Entrex Trapezoid.
But the Datascope came along bofore it, and made by
the same people, so it is work looking at.
The Entrex Datascope came along before the Trapezoid and a good
part of the game with the Trapezoid is understanding what is
different and what is the same. As we learn more, it becomes
apparent that the differences dominate, perhaps not in function but
in design. Here are some things we think we know:
- A system with a Datascope had only one terminal.
- A system with Trapezoids could have many terminals.
- The Datascope worked with a DG Nova and a special interface board.
- We don't know (or have) the interface board for the trapzoid.
- Both use the same connector, but the trapezoid has two.
- The Trapezoid does not work when connected in lieu of a datascope.
- Signals on the connector are very different.
The Datascope used a single logic board with no microprocessor.
Here is a photo of the logic board:
Note that date codes on the Datascope are 1975 and 1976.
Date codes on the Trapezoid interface board are 1980,
so the trapezoid came along about 5 years later.
The Trapezoid uses several boards and has a "backplane".
A functional trapezoid would have at least 2 boards, the processor
board and an interface board. We do have a schematic for the
Datascope!
The first page is a "title page", so there are actually only 3 pages
of schematics.
Manchester encoding
The schematic has annotations indicating that the data is transmitting to and
from the host using manchester encoding (this is not done on the later
Entrex trapezoid). Manchester encoding is designed so that a separate clock
is not needed, but the datascope does not try to recover the clock from the
data but uses an on board clock signal. For those who may be interested in
more details, the following links may be instructive:
Datascopes in the wild
The following image shows a data entry "sweatshop" somewhere in France.
Note that whatever the host computer was (generally a Data General Nova),
it had an interface board with up to 32 connections (one cable to each terminal).
So 32 terminals could be supported and Entrex was proud of it.
Note that the Entrex 480 was rebadged as the Nixdorf 620.
Feedback? Questions?
Drop me a line!
Tom's Computer Info / tom@mmto.org
