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"Analog jack" for digital line?

"Analog jack" for digital line?

"Analog jack" for digital line?

We asked for a number of rooms to be cabled for voice.

With two exceptions, all lines should be digital.

Looking at the wall jack (in one of the rooms that will have a digital line), I see that I cannot insert an RJ45 end.

The person who ran the lines said there is a cable for this and that when we are ready to move into these rooms he would take care of everything.

Does this sound right?

Can digital lines really use that type of jack?

RE: "Analog jack" for digital line?

Most digital phone systems only use 2 wires to connect to the phone. What you are probably seeing is a 6 pin rather than an 8 pin which is actually the correct way to do a voice jack. If you look at the cable from the phone, you will see it only has 6 pins on the connector. The only exception with most phone systems to this is if you are using IP phones, then they will use the larger 8 pin connectors into a data jack.

RE: "Analog jack" for digital line?

Middle two pins are the voice transmission. Two outside of that are -48vdc, to power some older phones (both analog and digital). Those power pins aren't used much anymore and usually a 6 pair .
The phone jack itself doesn't care whether the phone is digital or analog and if you look at the end of the RJ11 cord, many have only 1 pair going into your jack anyway. So in the end an RJ11 cord will work just fine for an analog phone with an RJ45 jack and same for digital, if the phone doesn't require power and most don't.

RE: "Analog jack" for digital line?

"Those power pins aren't used much anymore and usually a 6 pair."
Should read:
"Those power pins aren't used much anymore."

RE: "Analog jack" for digital line?

OK, but what about the difference with the ends?

The RJ45 is too large (wide) for the wall jack.

Wouldn't the RJ11 be two narrow for the jack under the phone?

RE: "Analog jack" for digital line?

Rj11 and rj12 should clip in to the base of the phone.

Rj11 would be 6 position 4 conductor.

rj12 would be 6 position 6 conductor.

Same physical size.


RE: "Analog jack" for digital line?

It would help to know what kind of phone system you have. Some older systems were 3 or 4 pairs.

jeff moss

RE: "Analog jack" for digital line?

Sure. It's Merlin Legend (Release 5 - according to the guide I have in front of me). The phones are MLX 10 or 20, like the one shown here:


I was able to plug a smaller RJ11 cable into one of these phones. The jack is notched in such a way that it will take either RJ11 or RJ45 (I'm not familiar with RJ12). This RJ11 would fit in the wall jack as well. But I'm not sure if that will actually function with a digital phone. (the phones in this wing aren't "live" yet so I could not test any further).

RE: "Analog jack" for digital line?

Do the phones you currently use have 1, 2, 3, or 4 pair line cords?
As the others have said, most digital systems only use 1 pair.
An 4 or 6 pin plug will fit in an 8 pin jack.

jeff moss

RE: "Analog jack" for digital line?

the phone cords that come with the phone system are RJ45, but you can replace them with RJ11 so that you can plug them into the smaller jacks.

"Friends,Romans,Countrymen lend me your ears I come to ask for help and to give it, lets not argue on who is best or worst lets just help each other"

RE: "Analog jack" for digital line?

I thought all Merlin phones of that era were 4 pair?  

jeff moss

RE: "Analog jack" for digital line?

Not sure myself (for Merlin phones of that era) but it looks like two pair is enough for digital anyway (and one pair for analog). The only unit that might need a full four pair is the console or "programming" phone unit.

Sound right?

RE: "Analog jack" for digital line?

the early merlins , 206 ,410, 820 , used 4 pairs,
merlin+  820 , 820D used also 4 pairs , but you could use 3 pairs , and also 2 pairs with a pwr. on the third pair

 Merlin 11 most used 3 pairs ,except the console & voice over busy stations
 Legends Hybrid stations 3 pairs, Mlx 2 pairs, Console 3 pairs,
 Magix 1 pair or 2 for MLX


RE: "Analog jack" for digital line?

Sounds like you need to leave the jacks alone and change the phone system!!! smile

RE: "Analog jack" for digital line?

Do the phones you currently use have 1, 2, 3, or 4 pair line cords?
As the others have said, most digital systems only use 1 pair.


The MLX phones (10 or 20) have RJ45 cables so 4 pair.

The others (I have an Avaya 6221 in front of me) have two pair.

Looks like 4 pair is overkill then and two pair RJ11 should do just fine (if I understand correctly).

RE: "Analog jack" for digital line?

MLX 10 16 & 28 can get by with 2 pairs  on a RJ45  pins 3456
console uses 3 pairs 345678 if it has the DSS  2 pairs other wise
 IT"S because in that era AT&T used 8 conductor  cords in all their difference phones and we would make the changes at the block  

RE: "Analog jack" for digital line?

1+ cvrbob - Legend phones (MLX series) use two center pair.  If the contractor wired correctly, the 6-pin jacks will work fine.  You MAY need to swap line cords if your phones have 8-pin plugs.  If swapping line cords, be sure to use two-pair cords.

RE: "Analog jack" for digital line?

Makes sense now!

jeff moss

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