Mike's PBX Cookbook

Connecting E1 / T1's


A 2 pair connection (TX/RX) between the service providers DSU and the PBX. It can use a number of different connection methods depending upon the service, provider, equipment, and location:

Be prepared to experiment a little, and/or swap the transmit and receive pairs. A Red "Near End Alarm" (NEA) indicates a local cabling problem, with the RX or both pairs open. A Yellow "Far End Alarm" (FEA) indicates the local TX pair is open.

DSU Pinouts:

A circuit can be presented on a DB-9 (E1) , DB-15 (T1), or RJ48/RJ45. The following table shows the pinouts for each:

DB-9 (E1) (NT8D7217E6)DB-15 (T1)CSU/DSU * (RJ48/RJ45) (T-568B)
2 - Black/Transmit1 - White/Transmit1 - Transmit (R1)
3 - Red/Transmit9 - Black/Transmit (could be 8)2 - Transmit (T1)
6 - Black/Receive3 - Red/Receive4 - Receive (R)
7 - White/Receive11 - Black/Receive (could be Yellow)5 - Receive (T)

* DSU/CSU = Data Service Unit/Channel Service Unit, eg, the PTT modem.

PBX hookup:

Media Gateways (and Option 11's) can use an NTBK04 cable, NTBK65 adapter, or a direct MDF connection.

NTBK65 UDT RJ48C breakout adaptor

RJ-48 Loopback
Loopback: pins 1 to 4, and 2 to 5

If you can't find an NTBK65 UDT RJ48C breakout adaptor (right), use pairs 23 (TX) and 24 (RX) on the MDF. If the circuit doesn't go green, just swap the TX/RX pairs.

Note: An RJ-48 is a keyed RJ-45. An RJ-45 connector will fit an RJ-48 jack, but the key on an RJ-48 connector will prevent it from plugging into an RJ-45 jack.

The following table shows the NTBK65 adaptor signal pin out:

25pr MDFRJ48CSignal(T-568B)
Pair 231RX Ring
-2RX Tip
 3n/c
Pair 244TX Ring
-5TX Tip
 6n/c 
 7n/c
 8n/c 

MDF Termination:

The NTBK65 is a replacement to the NTBK04 cable assembly. If neither are available, make the termination directly on the MDF block associated with the card slot using the following pinout. If the circuit doesn't go green, swap the TX/RX pairs:

Cable
Patching
Violet/GreenTransmit (TX)
- to network
TIP 0MDF/BIX
 Pair 23
Green/VioletRING 0
Violet/BrownReceive (RX)
- from network
TIP 1MDF/BIX
 Pair 24
Brown/VioletRING 1
Slate/VioletFrame GroundFGNDNot Used

RJ45 to DB-9F (E1) Adapter:

Large systems (51C/61C/81C) use a DB-9 (E1), or DB-15 (T1) connector, located at the rear of a network shelf .
The picture also shows an improvised RJ45 loopback adapter used for testing (blue and orange pairs looped)!

Use the following adapter configuration with an E1, DB-9 end on the PBX (to NTCK45AA on J5).
You may need to reverse the TX / RX pairs - or swap orange & blue with T-568B (568A or 568B).

Note: Most RJ45 to DB-9F Adapters use this colour
scheme, but yours may not! Always check it first!

RJ-45ColourDB-9
1Blue2
2Orange3
3Black
4Red6
5Green7
6Yellow
7Brown
8White

RJ45 to DB-15F (T1) Adapter:

Use the following adapter configuration with a T1, DB-15 end on the PBX.
You may need to reverse the TX / RX pairs - or swap orange & blue with T-568B (568A or 568B).

Note: Most RJ45 to DB-15F Adapters use this colour
scheme, but yours may not! Always check it first!

RJ-45ColourDB-15
1Blue1
2Orange9
3Black
4Red3
5Green11
6Yellow
7Brown
8White

Loopback Adaptors:

RJ-48 Loopback

Note: An RJ45 connector will fit an RJ48 jack, but the key on an
RJ48 connector will prevent it from plugging into an RJ45 jack.

Note the improvised loopback adapter in this picture!
Remember, the D channel will not establish on a loop test.

G.703 Balun:

G.703 Balun

An E1 maybe presented on two coaxial connectors (eg, BNC's), one each for TX and RX. A G.703 Balun is a bi-directional passive device (transformer) that converts unbalanced (75 ohm, BNC) to balanced (120 ohm, RJ45) signals. The RJ45 side uses the standard pairs: 1 & 2, and 4 & 5. If a circuit is presented on coaxial connectors, always use a balun with a matching impedance, eg: 75 to 120 ohm.


BNCRJ45(T-568B)
TX
(out)
1 - Transmit (R1)
2 - Transmit (T1)
RX
(in)
4 - Receive (R)
5 - Receive (T)


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