Girish Mahajan (Editor)

Plant test number

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In landline telephony, a plant test number or exchange is a number or group of numbers reserved for use by telephone installers to perform routine tests on an individual telephone line.

These include, but are not limited to:

  • Automatic number announcement circuit, a machine which announces the caller's own number
  • Loop around, a primitive conference call bridge
  • Milliwatt test, a standardised 1004 Hz, zero dBm sinusoidal test tone used to measure line quality and transmission loss between stations.
  • Ringback number, which causes the calling telephone to ring to verify an installation is working and the phone number routing properly.

    • Each country uses different codes. BT Linetest Facilities (for example) are available by ringing 17070 and a self-service test facility for subscribers is on 0800 800628.

    In the North American Numbering Plan, 958-xxxx and +1-NPA-959-xxxx are commonly reserved for local and long-distance test numbers (respectively). A few localities (including Winnipeg) reserve 959 only.

    References

    Plant test number Wikipedia
    (Text) CC BY-SA