A Milliwatt test (Milliwatt line) is a test method or test facility used in
telecommunications
Telecommunication is the transmission of information by various types of technologies over wire, radio, optical, or other electromagnetic systems. It has its origin in the desire of humans for communication over a distance greater than that fe ...
to measure line quality and transmission loss between stations or points in an analog telephone system.
The test consists of transmitting an analog sinusoidal signal at the frequency of 1004
Hz with the power level of 0 (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 ...
. By definition, this is the equivalent of a continuous power dissipation of 1 mW (
milliWatt
The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James Wat ...
), i.e., the power consumed if a voltage of 0.775
V(
RMS) is applied to a telephone line with 600
Ohm
Ohm (symbol Ω) is a unit of electrical resistance named after Georg Ohm.
Ohm or OHM may also refer to:
People
* Georg Ohm (1789–1854), German physicist and namesake of the term ''ohm''
* Germán Ohm (born 1936), Mexican boxer
* Jörg Ohm (b ...
nominal impedance.
[H.A. Quinn, et al., 'A New Standard Volume Indicator and Reference Level', Proceedings of the Institute of Radio Engineers, Volume 28 (1940)]
In the
Bell System
The Bell System was a system of telecommunication companies, led by the Bell Telephone Company and later by the American Telephone and Telegraph Company (AT&T), that dominated the telephone services industry in North America for over one hundr ...
, central offices provided this type of service on a dedicated telephone number (102 type Milliwatt line) for remote subscriber line testing. In conjunction, a second line (type 100 line) provided quiet termination. Various types of test lines were called "100", "102", "104" etc., because these numbers accessed the test line in
tandem office
A class-4, or tandem, telephone switch is a U.S. telephone company central office telephone exchange used to interconnect local exchange carrier offices for long distance communications in the public switched telephone network.
A class-4 swi ...
s in lieu of an area code.
In digital central office installations, the Milliwatt test facility was implemented using a synthesized version of the 1004
Hz signal, often called the
digital milliwatt. +1-(503)-697-1000 is an example of such a Milliwatt from a digital central office.
See also
*
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 sec ...
*
Plant test number
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 (NANP) reserves ...
*
Transmission level point
In telecommunication, a transmission level point (TLP) is a physical test point in an electronic circuit, typically a transmission channel, where a test signal may be inserted or measured.Whitham R. Reeve (1992) ''Subscriber Loop Signaling and Tr ...
References
{{Reflist
Telecommunications systems
Communication circuits
Telephony
Telephone numbers