Today I had a POTS line installed to my 66 block/DEMARC. I need to hook-up a phone for this line for my boss. I'm assuming I can just wire the appropriate patch cable into the 66 block, patch it to his phone port and plug the phone in on the other end in his office.

After inspecting the 66 block in the telco room I realize I don't really understand how it works. Here's an image of the 66 block, where the phone line has been installed into 'slot #2'.

punch down box

This is the patch cable I want to use. It's just 4 wires, open on one end, and an RJ45 on the other. (Image because the colors look atypical)

patch cable

Is my assumption in how to hook up this line correct?

If so, which wires do I put into which terminals specifically? (That's what I don't understand.)

Additional note: I do not have any sort of tone/dial tone detection equipment, the line is installed to "slot #2."

  • Something I don't understand: Is a phone line already installed from somewhere on the 66 block to the boss's office? Or is the cable pictured above something you're running from the telco room to the office (wall jack)? Apr 15, 2015 at 0:29
  • And those four little metal tabs are jumpers. Each of those four rows are connected in parallel, respectively. Apr 15, 2015 at 0:34
  • The phone company terminated the phone line at 'slot #2' (i guess the 3rd/4th row from the top) on the 66 block. From there it's up to me to do the rest. The wall jack in my boss' office goes to a 48-port patch panel in the telco room. So I just have to go from the 66 block to the corresponding port on my patch panel. (Why I choose a patch cable with an RJ45; i know ultimately rj11/rj45 is trivial) Anyway I followed the directions provided by @Todd Wilcox below, and it's working great!
    – malfy
    Apr 15, 2015 at 16:14

1 Answer 1


The black and yellow pair should be terminated on the pins just to the right of where the phone company terminated the pair. You can look at the pair above the pair you want and see someone has terminated something right above where you want to terminate.

That's called a 66 block and it has 50 rows of terminals by four columns. Each row in the left two columns are connected and each row in the right two columns is connected, but the left and right half are not connected.

So you need to go to the second column from the left and the third and fourth rows.

Now it sort of matters which one you terminate on the third row and which one you terminate on the fourth, but for your situation it's not worth worrying about.

  • Thanks a bunch! Worked exactly as you described. Additionally thanks for explaining how the 66 block works.
    – malfy
    Apr 15, 2015 at 14:59

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