Re: Pinout for current loop interface
On Sat, Aug 17, 2019 at 12:14 PM Charles via cctalk wrote: > >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. > > Thanks for the comments... I asked mostly because the ADM-3A has both RS-232 > and current loop interfaces built-in Given the problem you are trying to solve, if I were in your shoes, since I have a lot of DEC gear, I would standardize on 8-pin Mate-n-Lok connectors, but I have numerous devices already so equipped (ASR33, VT52, VT220, VT100 w/20mA option, PDP-8 (various), DZ11 breakout panel...) Since I was just holding an original IBM PC serial interface (as discussed above), I should probably bite the bullet and make a DB25-8-pin-Mate-n-Lok cable for it, just in case (I happen to have a couple of options for using ISA cards on Amigas, so it's even multi-platform). I happen to have a stash of the shells. What I should do is buy a bag of the pins and get a reel of the 4-wire (R/G/B/W) cable that was commonly used in the DEC world, then I'd be all set. DB25s are easier to come by, but as has been mentioned, there's not one way to wire them up and having a large stack of magic pin-swabber cables is kind of a pain. -ethan
Re: Pinout for current loop interface
You haven't lived until you have played with live long-line teletype current loop circuits. In my first job as an FE on a Univac that was a store and forward message switcher, we had racks of mercury relays feeding the teletype lines, which ran at 130VDC to give the current needed to get to the next hop! Working in that rack could result in some very sudden surpsies! cheers, Nigel On 17/08/2019 14:50, Charles via cctalk wrote: In my prior life as an EE, I had to do it many times (early 80's)... I may be nostalgic, but not THAT nostalgic :) -Original Message- From: Chris Hanson Sent: Saturday, August 17, 2019 1:37 PM To: Charles ; General Discussion: On-Topic and Off-Topic Posts Subject: Re: Pinout for current loop interface On Aug 17, 2019, at 9:14 AM, Charles via cctalk wrote: I just hate having to make a custom cable for every terminal and computer I own or work with ;) Ah, but isn’t doing what so many before you have had to part of the charm? :) -- Chris --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus -- Nigel Johnson MSc., MIEEE VE3ID/G4AJQ/VA3MCU Amateur Radio, the origin of the open-source concept! You can reach me by voice on Skype: TILBURY2591 If time travel ever will be possible, it already is. Ask me again yesterday This e-mail is not and cannot, by its nature, be confidential. En route from me to you, it will pass across the public Internet, easily readable by any number of system administrators along the way. Nigel Johnson Please consider the environment when deciding if you really need to print this message
Re: Pinout for current loop interface
On Aug 17, 2019, at 9:14 AM, Charles via cctalk wrote: > I just hate having to make a custom cable for every terminal and computer I > own or work with ;) Ah, but isn’t doing what so many before you have had to part of the charm? :) -- Chris
Re: Pinout for current loop interface
> > Thanks for the comments... I asked mostly because the ADM-3A has both > RS-232 > and current loop interfaces built-in (on the same female DB-25), selected > by > one of the > DIP switches. > > I just hate having to make a custom cable for every terminal and computer I > own or work > I have some specific pinouts for current loop on my site... for dec pdp 11/05, swtpc 6800, altair 680, and rs232 to current loop conversion. Vintagecomputer.net Bill >
Re: Pinout for current loop interface
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. Thanks for the comments... I asked mostly because the ADM-3A has both RS-232 and current loop interfaces built-in (on the same female DB-25), selected by one of the DIP switches. I just hate having to make a custom cable for every terminal and computer I own or work with ;) -Charles --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
Re: Pinout for current loop interface
On Sat, Aug 17, 2019 at 4:38 PM Noel Chiappa via cctalk wrote: > > > 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. 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
RE: Pinout for current loop interface
Ask Continental Computers, they should still have some. Talk to Lidan. 310-416-1200. -Original Message- From: cctalk [mailto:cctalk-boun...@classiccmp.org] On Behalf Of Noel Chiappa via cctalk Sent: Saturday, August 17, 2019 10:39 AM To: cctalk@classiccmp.org Cc: j...@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 --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
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
Re: Pinout for current loop interface
On Fri, Aug 16, 2019, 10:56 PM Ethan Dicks via cctalk wrote: > On Sat, Aug 17, 2019 at 12:12 AM Charles via cctalk > wrote: > > Is there any standard pinout for 20 ma current loop using a DB-25 > connector, > > analogous to the well-documents RS-232 serial interface? > > From checking a couple of devices, I don't think so. Here's how the > original IBM Async adapter for the 5150 did it... > > Pin 18 +receive current loop data > Pin 25 -receive current loop return > Pin 11 -transmit current loop data > Pin 9 +transmit current loop return > > One BlackBox adapter I found used different pins. > > > The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. > > I'm used to using 15 and 17 for sync serial clock. They are typically > NC for async. 23-25 have alternate uses that are, again, typically > NC. (I've never seen a device that used pin 25 for 'test'). There are > Sun workstations that have two serial ports over one DB25 which might > be the only use of the "B" pins I've encountered. > The DEC rainbow has B pins for talking to a modem dialer via a special cable... but it is basically useless for anything other than a few characters. Warner >
Re: Pinout for current loop interface
On Sat, Aug 17, 2019 at 12:12 AM Charles via cctalk wrote: > Is there any standard pinout for 20 ma current loop using a DB-25 connector, > analogous to the well-documents RS-232 serial interface? >From checking a couple of devices, I don't think so. Here's how the original IBM Async adapter for the 5150 did it... Pin 18 +receive current loop data Pin 25 -receive current loop return Pin 11 -transmit current loop data Pin 9 +transmit current loop return One BlackBox adapter I found used different pins. > The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. I'm used to using 15 and 17 for sync serial clock. They are typically NC for async. 23-25 have alternate uses that are, again, typically NC. (I've never seen a device that used pin 25 for 'test'). There are Sun workstations that have two serial ports over one DB25 which might be the only use of the "B" pins I've encountered. -ethan
Pinout for current loop interface
Is there any standard pinout for 20 ma current loop using a DB-25 connector, analogous to the well-documents RS-232 serial interface? My PDP-8/A drives an ASR-33, and having just restored an ADM-3A I want to be able to unplug the TTY and plug in the ADM. I somewhat arbitrarily put the transmit data + on pin 2 and receive + on pin 3, and picked two uncommitted RS-232 pins for the - legs of both loops. The ADM-3A receives on pins 23 & 25, and transmits on pins 24 & 17. Polarity doesn't matter since both pairs use bridge rectifiers. If this is some kind of de facto standard, I'll change the bulkhead connector on the PDP-8 and the TTY to match. Otherwise I'll just make yet another unique cable to hook up the ADM-3A to the PDP-8 as it's wired. Or would you recommend I use a different connector entirely? The reason I used the DB-25 to begin with is that I had a DEC rack-mount plate that already takes one. Maybe a Jones 4-pin would make more sense. thanks for any tips. -Charles --- This email has been checked for viruses by Avast antivirus software. https://www.avast.com/antivirus
