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Modular connector snafu

O

Oppie

Jan 1, 1970
0
Is there any standard for modular phone connectors? I suspect not since was
looking up the 4p4c headset jack (referred to as RJ9, RJ10 and RJ22), I
don't recall that any of the manufacturers indicated pin numbers. Of course,
it also is complicated by whether the connecting cable is 1:1 or cross-over.
RJ11 is often confused as it is wider and though has also 4 circuits
connected, is actually spaced for 6 circuits.

Was connecting up a demo board this morning that used the 4p4c modular
connector for the CAN bus. Cannibalized a connector and cord from an old
telset. Became a smoke generator inadvertently. Luckily, no damage and all
worked after I mirrored one of the sockets. The telco handset cord was
cross-over type and luckily had enough impedance to get hot rather than
killing anything else (5V and ground in it).
 
S

Spehro Pefhany

Jan 1, 1970
0
Is there any standard for modular phone connectors? I suspect not since was
looking up the 4p4c headset jack (referred to as RJ9, RJ10 and RJ22), I
don't recall that any of the manufacturers indicated pin numbers. Of course,
it also is complicated by whether the connecting cable is 1:1 or cross-over.
RJ11 is often confused as it is wider and though has also 4 circuits
connected, is actually spaced for 6 circuits.

Was connecting up a demo board this morning that used the 4p4c modular
connector for the CAN bus. Cannibalized a connector and cord from an old
telset. Became a smoke generator inadvertently. Luckily, no damage and all
worked after I mirrored one of the sockets. The telco handset cord was
cross-over type and luckily had enough impedance to get hot rather than
killing anything else (5V and ground in it).

These any help?

http://en.wikipedia.org/wiki/4P4C#4P4C

"However, if the wire pair for the handset transducer and the wire
pair for the handset microphone are each wired in a crossover
arrangement, then both the transducer and microphone will function
correctly; even if the handset has an electret microphone. Most
telephone handset cords (cable assemblies) are wired this way."

As the Wiki article points out, the handset connectors have nothing to
do (directly) with the PSTN so they are not registered.

http://www.belfuse.com/Data/UploadedFiles/MN300018.pdf
 
S

Spehro Pefhany

Jan 1, 1970
0
A connection standard might have helped, but it still helps to use a
DVM to check your wiring and connections. Otherwise, look into fuses
and current limiters.

Also, you can just look into the ends of the clear polycarbonate
plugs- you can see the wire color codes.

As Jeff points out, the tools are available from all sorts of places
and can be very inexpensive (starting at under $10, up to a few
hundred or more for production hand tools).

Modular jacks are great- cheap, pretty reliable, positive retention,
built in strain relief, easily and cheaply field-terminated. Too bad
the female connectors are so enormous.
 
J

josephkk

Jan 1, 1970
0
I never noticed but I'm not surprised. I just checked the pin
numbering on my various Rotomola radios (Maxtrac, Radius, SP50,
MCS2000, etc that use an RJ45 mic connectors. They're all numbered
backwards. Tradition must be maintained, even if it's wrong.

In about 1993(?), I stupidly was involved in a proposed standards
group trying to hammer out a standard for the pinout and connections
for RS-232 devices (mostly terminals, modems, and printers) using the
RJ-45 connector. The problem was that about half of the manufacturers
involved had numbered the 8 pins one way or the other. There was one
vendor that even labeled the pins A thru H. Since everyone wanted to
move on to more important arguments, it was decided to number from
left to right, gold pins up, as viewed from the front of the
receptacle. To the best of my knowledge, that became the de facto
standard (because the proposed group never became official). It was
amazing that the numbering scheme was ever accepted as there were
numerous unsettled issues such as symmetrical DTE/DCE wiring and using
4/6 pin and 10 pin (RJ50) connectors. Proponents wanted the pins
numbered from the center pins outward (odd numbers to the left) so
that larger and smaller connectors could use the same pin numbers for
the same functions. These were the same people and same logic that
gave us the even stranger pin numbering found on DIN circular
connectors.

Incidentally, in 1980 or so, HP drafting had managed to renumber the
common DB25 connector on several pieces of RF test equipment. This
was despite the numbers being printed on the connector. I was the one
that noticed and brought it to their attention. There were several
discussions where I had to convince a suit that this really was a
problem. I got nowhere until I offered to wire the mating plug in
accordance to the printed documentation instead of the connector
standard and report on what blows up. That problem was handed to an
HP engineer who wisely suggested that a manual addendum would be
cheaper and easier than having HP sued by an irate customer. Addendums
to the manuals with the correct pin numbering and a field service note
was issued. At that point, I became suspicious and found several
other pieces of test equipment that had misnumbered pins on some
connectors. I passed on the bad news, but left the company before I
could find out if anything useful had happened.


Check out TIA-561

also:

http://www.dcbnet.com/notes/eia561.html

There it is.

?-)
 
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