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Wiring a Single RJ11 Serial Jack

Introduction

Most serial links at Apache Point Observatory consist of two sets of eight 6-position 6-wire RJ11 (sometimes called RJ12) jacks, joined by one custom-manufactured Telco cable. These links are easy to make and modify. But sometimes it is wasteful to have eight serial connections in one area, so we have also provided a way to make single serial links. Each link consist of a single hand-wired RJ11 jack at one end, attached to one of a set of eight RJ11 jacks at the other end, via a punchdown block (as shown in figure 1). This document describes how to make single serial links.


Figure 1: The Basic Layout.

Directions

  • Choose an available harmonica or set of jacks in a patch panel. The jacks must meet the specifications given here.
  • If the jacks aren't already connected to a punchdown block, do so as follows (see figure 1):
    • Choose a punchdown block that meets the specifications given here.
    • Connect the 8 pre-wired RJ11 jacks to the punchdown block using an APO Custom Telco Cable (described elsewhere). They are easy to spot: unlike standard cables, they have a female Telco connector at each end.
  • Choose a free RJ11 jack from the harmonica or patch panel.
  • Find the corresponding first row of the punchdown block, using the "Starting Row" Table. You will punch a wire into this row and each of the next five rows below it.
  • Write down the colors of the three pairs of wires in Table 2. List them in any order you like, but maintain the wire pairing as shown.
  • Punch the six wires into the appropriate rows of the punchdown block, as shown in the Table 2.
  • At the other end of the cable, attach the six wires to the hand-wired RJ11 jack, as per Table 2.

Starting Row Of Punchdown Block

RJ11 Jack #

Starting Row of Punchdown Block

1

1

2

7

3

13

4

19

5

25

6

31

7

37

8

43

*Row 1 is attached to pin 26 of the Telco connector. The full specification is given here.

Wiring

Wire Color
You choose, but preserve the pairing.

Punchdown Row for RJ11 Jack #1. See starting row table for other jacks.

RJ11 Pin

Pair 1

1

4

4

5

Pair 2

2

3

3

2

Pair 3

5

1

6

6


RJ11 Pin Numbers

Specifications for the Punchdown Block

Punchdown block is 66M style with attached male Telco connector. Male Telco connectors are a bit rare on punchdown blocks, but are available. The block should be wired as follows (this is, or was, a standard).

Punchdown Row

Telco Pin

1

26

2

1

3

27

4

2

5

28

6

3

...

...