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

[erco]

> 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:

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]

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. 

[erco]

The RJ45 <-> amphenol converter boards I made assume ethernet style T568B cable wiring, as opposed to telco/USOC style.
Telco style, the pairs start on the center pair and expand outward. Ethernet style is similar for the inner 2 pairs, but the outer 2 pairs break that pattern, as one can see in this diagram:
     

Ethernet style cables are the easiest/cheapest to get premade these days, which is why I chose to use that for my converter boards.

If you use the harmonicas, check their wiring, so if they use, for instance, telco/USOC style, make sure your cables are wired to follow that same wiring standard to ensure the 1A2 voice pairs end up on actual physical twisted pairs in your cables. Or if it's ethernet style, it should work fine as long as you follow the same ethernet style for the cables. If you get it wrong, the signals will still go through, it's just those outer pairs might end up loosing the noise cancelling benefits of twisted pairs.

[erco]

An update about this:

>  [..] 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[..]

I actually do sell these now; made a page for them here: https://www.seriss.com/1a2-ksu/amphenol-to-rj-45/

Current prices as of this writing for these adapters: $85 for the pair ($35 for the adapter board that plugs into the ksu, $50 for the adapter board that connects to the phone set, and your long run of RJ45 cabling between the two). To inquire for details, email er...@seriss.com and set the Subject: of the message to "RJ45/Amphenol adapter inquiry".