Plant test number
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[1]
- Loop around, a primitive conference call bridge[2]
- 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.
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.[3]
Each country uses different codes. BT Linetest Facilities (for example) are available by ringing 17070[4] and a self-service test facility for subscribers is on 0800 800628[5].
References
- ^ http://www.artofhacking.com/tucops/phreak/callerid/live/aoh_anac.htm
- ^ http://home.ptd.net/~n3cvj/looplines.htm
- ^ Plant test exchange prefixes appear in the list of CO Code assignments (per area code) at http://nanpa.com (US) and http://cnac.ca (Canada) but the individual numbers are unpublished by design, as they're intended for installers only.
- ^ http://www.howtofixanything.co.uk/howto-btlinetestfacility.html
- ^ http://www.redcare.bt.com/PDF/Installations_Support/Self%20Service%20Line%20Test%20V1.pdf