17 Aug
2019
17 Aug
'19
8:38 a.m.
From: Charles Morris
Is there any standard pinout for 20 ma current loop
using a DB-25
connector, analogous to the well-documents RS-232 serial interface?
...
Or would you recommend I use a different connector entirely? .. Maybe a
Jones 4-pin would make more sense.
I've never heard of people using DB25 for 20mA, at least historically,
contemporaneous with its widespread actual use. E.g. DEC universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.
Although I have the part numbers for both the male and female 8-pin shells,
they are no longer in production, and are getting hard to find.
Nothing precludes us from establishing a spec for 20mA via a DB25, of course
- especially if a set of pins can be found whih will not cause damage if such
a connector is plugged into an EIA connector by accident.
As 'idiot proof' engineering, I'd be inclined to use some other connector (no
suggestion from me as to what), but I can understand that people might prefer
to use DB25 (which everyone has, and are easy to find).
Noel
17 Aug
17 Aug
8:51 a.m.
Ask Continental Computers, they should still have some. Talk to Lidan.
310-416-1200.
-----Original Message-----
From: cctalk [mailto:cctalk-bounces at classiccmp.org] On Behalf Of Noel
Chiappa via cctalk
Sent: Saturday, August 17, 2019 10:39 AM
To: cctalk at classiccmp.org
Cc: jnc at mercury.lcs.mit.edu
Subject: Re: Pinout for current loop interface
From: Charles Morris
Is there any standard pinout for 20 ma current loop
using a DB-25
connector, analogous to the well-documents RS-232 serial interface?
...
Or would you recommend I use a different connector entirely? .. Maybe
a
Jones 4-pin would make more sense.
I've never heard of people using DB25 for 20mA, at least historically,
contemporaneous with its widespread actual use. E.g. DEC universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.
Although I have the part numbers for both the male and female 8-pin shells,
they are no longer in production, and are getting hard to find.
Nothing precludes us from establishing a spec for 20mA via a DB25, of course
- especially if a set of pins can be found whih will not cause damage if
such
a connector is plugged into an EIA connector by accident.
As 'idiot proof' engineering, I'd be inclined to use some other connector
(no
suggestion from me as to what), but I can understand that people might
prefer
to use DB25 (which everyone has, and are easy to find).
Noel
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8:55 a.m.
On Sat, Aug 17, 2019 at 4:38 PM Noel Chiappa via cctalk
<cctalk at classiccmp.org> wrote:
Looking around here I think it is safe to say that there is no
standard. I've got :
3 different wirings on DB25 connectors (the IBM PC serial port which has already
been mentioned, the original Apple ][ bitbanger serial card and a Miniterm 1203
portable terminal which can be strapped internally to put a current
loop interface
on pins 13-16 of the DB25). In all cases there's a subset of the RS232
interface on
the expected pins
Those flat 8-pin mate-n-lock connectors that DEC used
An 8 pin mini-Jones connector (Intellec 8)
DE9 (on a 'Ferret' peripheral tester thing) And a different wiring
on a cable that came with my Data Dynamics 390 (Teletype
Model 33 mechanical parts with Data Dynamics electronics)
5 pin 240 degree DIN socket (on an acoustic modem)
GPO Plug 420/Jack 84 (or Jack 95). This is the old 4 contact
cylindrical plug/socket used on UK telephone systems in the
1960s/1970s and seems to be used for current loop by UK
universities at the time.
Screw terminal barrier strips.
-tony
From: Charles Morris
Is there any standard pinout for 20 ma current
loop using a DB-25
connector, analogous to the well-documents RS-232 serial interface?
...
Or would you recommend I use a different connector entirely? .. Maybe a
Jones 4-pin would make more sense.
I've never heard of people using DB25 for 20mA, at least historically,
contemporaneous with its widespread actual use. E.g. DEC universally used
'flat' 8-pin Mate-n-Lok connectors for 20mA serial connections.
1954
days inactive
1954
days old
2 comments
3 participants
participants (3)
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