In telecommunications, a plant test number is a telephone number reserved for use by telephone installers or other workers to test an individual telephone line. Test number are typically unlisted.
The
North American Numbering Plan
The North American Numbering Plan (NANP) is a telephone numbering plan for twenty-five regions in twenty countries, primarily in North America and the Caribbean. This group is historically known as World Zone 1 and has the international callin ...
(NANP) reserves the exchange (''central office'') prefixes ''958'' and ''959'' for plant testing.
[''Telcordia Notes on the Network'', Telcordia Technologies, Special Report SR-2275 Issue 4 (October 2000), Section 8.2.5, p.8-8]
Central office code 958 is intended for communications between switching centers. Central office code 959 with three or four additional digits is dedicated for access to office test lines in local exchange carrier (LEC) and interoffice carrier (IC) central offices. The specifications define several test features for line conditions, such as quiet line and busy line, and test tones transmitted to callers.
The tests available for plant testing include
*
Automatic number announcement circuit
An automatic number announcement circuit (ANAC) is a component of a central office of a telephone company that provides a service to installation and service technicians to determine the telephone number of a telephone line. The facility has a tel ...
, a machine which announces the caller's number
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Loop around
A loop line or loop around is a telephone company test circuit. The circuit has two associated phone numbers. When one side of the loop is called (side A), the caller receives a test tone of approximately 1000 Hz ( milliwatt test). When the se ...
, a primitive conference call bridge
*
Milliwatt test A Milliwatt test (Milliwatt line) is a test method or test facility used in telecommunications to measure line quality and transmission loss between stations or points in an analog telephone system.
The test consists of transmitting an analog sinus ...
, a standardized 1004 Hz, zero
dBm
DBM or dbm may refer to:
Science and technology
* dBm, a unit for power measurement
* DBM (computing), family of key-value database engines including dbm, ndbm, gdbm, and Berkeley DB
* Database Manager (DBM), a component of 1987's ''Extended Edi ...
sinusoidal test tone used to measure line quality and
transmission loss
Transmission loss (TL) in general describes the accumulated decrease in intensity of a waveform energy as a wave propagates outwards from a source, or as it propagates through a certain area or through a certain type of structure.
It is a termino ...
between stations.
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Ringback number
A ringback number is a telephone number for a telephone line that automatically calls the line that the call was placed from, after the caller has hung up. The typical use of this facility is by telephone company technicians for testing a new insta ...
, which causes the calling telephone to ring to verify an installation is working and the phone number routing properly.
Some localities reserve 959 only.
Each country uses different codes.
BT Linetest Facilities (for example) are available by ringing 17070 and a self-service test facility for subscribers is no longer available.
References
{{reflist
Telephone numbers
Communication circuits