Need a long serial port for an ELK


Active Member
Hi --

So, the good news is that I have a "basic" M1 Gold security system installed (cue fanfare!) and some very basic automation rules. The bad news is that I bench-programmed the ELK in the 2nd floor office, but installed it in the wire closet in the basement. Since the computer I used is upstairs, I have no great options to change the programming.

I wired cat5 everywhere, and it would seem like a simple task to modify a cat5 cable to really be a serial cable. Alas, I'm not a hobby-boardist, so all the stuff I found on google is over-my-head.

Anyone know (or can point me to) a guide for building a RS-232 serial cable out of a cat 5 cable? Or, even better, a place that sells RS-232 plugs for cat-5 cables? :)

Alternatively,is there a good USB adapter that works over cat-5 cables?


PS -- Yeah, I know... elk ethernet module... and I might do that eventually, but I figure these plugs should cost like $2 each.
Look on page 7 of the M1 installation manual. There is a serial cable diagram. Basically PINs 2 , 3 , and 5 are used to make a serial cable.
Spanky --

So... I can cut an existing serial cable in half and just connect the existing wires to a cat5? Do they sell RJ45-->RS232 connectors? (eg: where an ethernet plug is plugged in on one end, and a serial cable comes out the back?)

Thank you!
If you're looking for an adapter like that, check out I've never looked for that specific adapter but they have tons of stuff like that ... and for cheap. They've become my favorite place for cables, ends, adapters, etc.
If you already have Cat5 runs (and terminated to RJ-45 plugs) then just use DB-9 to RJ-45 adapters such as the ones shown HERE.

Just look in the Elk manual to see if pins 2 and 3 are "crossed" or "straight thru" for the serial connection (elk to computer). Then just use three pins of these adapters (pins 2, 3, and 5 of the DB-9).

I do this for all my serial connections from my computer to hardware in my wiring closet such as my Caddx NX8e, Ocelot, and PH Anderson A-D converter. (I actually have all three working over one Cat5e connection :) ).
I use DB9->RJ45 converters as well (but use phone wire for the actual connection tho), and works great. I did this for my W800RF32, Elk M1 main serial port, Ocelot (all use 3 pins) and UPB PIM (4 pins).
Randy, BSR, and E --

Thank you! I'm all over those adapters. They look easy enough that even someone like me (lousy with a soldering gun) can make it work!
I don't even use a soldering gun, you just have to make sure you crimp the rj45 head correctly.
electron said:
I don't even use a soldering gun, you just have to make sure you crimp the rj45 head correctly.
You crimp the cable a special way? doesn't that make it easy to use the wrong cable for the wrong device? I thought you would pin the db9-rj45 adapter differently depending upon the device and using standard cables?
I don't use cat5 for my cable, I use phonewire, so it's different. I also have the RJ45 adapters that let me select which pins goes where in the serial port part, so if you start playing with that, you have to verify your cable is going to work, especially if you don't have access to a pin extraction tool (learned that the hard way)