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:
Each country uses different codes. BT Linetest Facilities are available by ringing 17070 and a self-service test facility for subscribers is no longer available.
In the North American Numbering Plan, 958-xxxx and +1-NPA-959-xxxx are commonly reserved for local and long-distance test numbers. A few localities reserve 959 only.