User's questions: Can network cables (cat-5) be used for 1a2?

Skip to first unread message


Jul 25, 2019, 9:48:46 PM7/25/19
to seriss-1a2-ksu
> I want to place my phones in other rooms, far apart.
> Is there a way to avoid running 25 pair cables for each phone?

     Yes, you can use regular cat-5 network cables to route 1a2 signals.

     For each 1a2 line, 6 conductors are needed (3 pairs). Cat5 cables have 8 conductors (4 pairs),
     so if you work out the wiring just right, you can sneak in the bells and buzzers on the extra pair.

     Just keep each 1A2 pair you need on a matching twisted pair in the network cables, to preserve
     noise immunity.. especially for the T/R pair.

     Converting from 25PR to/from RJ-45 can be done several ways:

* Use 66 blocks to convert to/from the network cable runs
  With this, you can punch down the wire pairs how ever you want.

* Use RJ-45 <-> Amphenol "harmonicas" to convert to/from CAT-5 cabling.
  These are typically pre-wired in ways that work but won't leverage the signal paths
  optimally, causing you to use more cables than might be needed.

* Make some custom boards for common 1a2 signals (like the ones I made shown below)

     Because I could, I made some custom boards to handle this. I don't sell these, I just made them
     for my own office network:

[Linked Image]

[Linked Image]
The first pic is the "KEY SYSTEM" (KSU) end, plugging straight into the female amphenols on the KSU board, starting a long 50' run of two cat-5 cables.
The second pic is the "PHONE" end, which converts the other end of the cat-5 cables back into an amphenol female that the phone can plug into.

These two miniature boards work as a pair, and when 3 cat-5 cables are used, can handle 3 CO lines plus intercom, bells and buzzers.
In these photos I'm just using 2 cat5 cables for lines 1+2 with bells. No intercom/buzzer unless I add another 50' cat5 cable.

As mentioned this can be done with 66 blocks, but it sure is easier with specialized hardware like amphenol <-> RJ-45 harmonicas.

John Stancliff

Jan 29, 2020, 10:37:35 PM1/29/20
to seriss-1a2-ksu
on my system Cat 5 cables is all I use. I have 25 pair cabling to the jacks, but the cords on the phones have been changed to Cat 5 to make them more residential. 
Reply all
Reply to author
0 new messages