Tieline Technologies

X.21 in Australia

Telstra’s DDS Fastway is a point-to-point service subscriber service that can be used to connect two Tieline codecs with X.21 plug-in modules between all major Australian capital cities and a variety of regional areas.

Data speeds vary but 256k connections are most commonly used by Tieline customers.

 ------ DDS Fastway Solution

Tieline X.21 Solutions using DDS Fastway  


Equipment Required

  • A Tieline codec with a Tieline X.21 plug-in module at both ends of the link.
  • A fully installed DDS Fastway service with a Telstra supplied Network Terminating Unit (NTU-4S) at each end of the link.
  • A straight-through D15 male to D15 female X.21 cable (Note: This cable can be purchased from Altronics in Australia or click here to download pin-outs for connectors).

 ------ DB15 cable

Tieline X.21 Plug-in Module and DB15 Male to DB15 Female Cable  


Programming the Tieline Codec for DDS Fastway Connections

  1. Insert a Tieline X.21 module into the Tieline codec and connect power.
  2. Attach a straight-through DB15 cable from the Tieline X.21 module to the Telstra NTU-4S.

     ------ NTU-S4 DB15 connection

  3. Plug the Telstra DDS Fastway cable with an RJ-45 connector into the “SHDSL” port on the rear of the NTU-4S.

     ------ Telstra NTU-S4 lights

  4. Check that there are four green LEDs displayed on the front of the NTU-4S.
  5. Press SOFTKEY 3 [Wiz] > [OK] and use the codec wizard to select [Algorithm (MusicPlus or MPEG)] > [Link Type (X21 >X21)] > [Bitrate (256000)] > [Call Control  (Permanent Link)] > [Configured (OK)]

The codec is now configured for X.21 over DDS Fastway.

Important Note: The “Bitrate” programmed via the codec wizard must match the data rate of the DDS Fastway service that you have ordered. In our example this is 256Kbps.  

Dialing and Hanging Up the Connection

After correctly programming the codec for X.21 the connection screen should display [X.21 > Dial/Answer].  

 ------ X21 pre-connection screen

Press the “ENTER/DIAL” button on the keypad to create a connection.

The call must be manually answered at the other codec by pressing the "ANSWER" key on the keypad. The connection screen displays the bit rate of the connection and the algorithm being used. In the example shown the bit rate is 256Kbps and the algorithm is MusicPLUS.

 ------ x21 connection screen

To hang up the connection simply press the “HANG UP” button on the keypad of either codec. Once you have connected successfully you can reconnect automatically thereafter by using the "ENTER/DIAL" button on either codec.