I just found that a piece of hardware I would like to connect via a serial port uses a non-standard hardware connection.

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One end is a female DB9 the other is what I think is an "old" telephone connector, but I can't seem to find the name of it. Here is the pinout of both the connectors from the manual for the device

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What is the name of this 4-wire/4-pin connector?

  • \$\begingroup\$ Looks like an RJ-45 to me, just off-hand. Often used with phones. If I were looking for a small, cheap, widely available connector that can withstand lots of connect/disconnect operations and do well... I might choose that. \$\endgroup\$ – jonk Mar 1 '17 at 18:34
  • \$\begingroup\$ Actually I seemed to have fixed my google queries and found now that it is most likely a 6P4C connector?.. \$\endgroup\$ – KDecker Mar 1 '17 at 18:35
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    \$\begingroup\$ Your "6P4C" is an RJ-11 \$\endgroup\$ – brhans Mar 1 '17 at 18:39
  • \$\begingroup\$ @brhans Yeah. That one, too! I use both and forgot the other name for the moment. Thanks for the catch. Mostly, I've been using the RJ-45 lately, so that stuck in my mind. It's not usually used in phones, though. Just the RJ-11. \$\endgroup\$ – jonk Mar 1 '17 at 18:41
  • \$\begingroup\$ Actually, the 8P8P modular jack (RJ45) is now being used for telephone more than ever. IP phones connect to a network and use 8P8P modular plugs. \$\endgroup\$ – MEZLAW Mar 7 '17 at 14:21

That is a 6P4P modular plug (6 position 4 pin) often mistakenly referred to as an RJ11. An RJ45 was also mentioned in the answers. RJ45 is often incorrectly used for 8P8P (8 position 8 pin) modular jack. RJ stands for registered jack and each number used after it refers to the wiring scheme originally used. RJ11 and RJ45 have been used incorrectly for so long they are now excepted terms much in the same way "scotch" tape is used for any "cellophane" tape.

You should look at the specs for that piece of hardware and see if they have a wiring scheme for their equipment. It depends on what you are connecting to that serial port and how you plan to use it. Some things to consider; is it DTE or DCE, will you need to used flow control, what is the baud rate going to be, does your cable need to be a "null" for what you are doing such as programming VIA the serial port.

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