In digital telephony

Digital telephony

Digital telephony is the use of digital electronics in the provision of digital telephone services and systems. Since the 1960s a digital core network has almost entirely replaced the old analog system, and much of the access network has also been digitized...

, the digital milliwatt is a standard test signal

Standard test signal

In telecommunication, a standard test signal is a single-frequency signal with standardized level used for testing the peak power transmission capability and for measuring the total harmonic distortion of circuits or parts of an electric circuit....

 consisting of eight 8-bit

Bit

A bit is the basic unit of information in computing and telecommunications; it is the amount of information stored by a digital device or other physical system that exists in one of two possible distinct states...

 words corresponding to one pulse-code modulated cycle of a sinusoidal signal approximately 1 kHz in frequency

Frequency

Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...

 and one milliwatt in power

Power (physics)

In physics, power is the rate at which energy is transferred, used, or transformed. For example, the rate at which a light bulb transforms electrical energy into heat and light is measured in watts—the more wattage, the more power, or equivalently the more electrical energy is used per unit...

.

The digital milliwatt is stored in ROM

Read-only memory

Read-only memory is a class of storage medium used in computers and other electronic devices. Data stored in ROM cannot be modified, or can be modified only slowly or with difficulty, so it is mainly used to distribute firmware .In its strictest sense, ROM refers only...

. A continuous signal of arbitrary length, i.e. an indefinite number of cycles, may be realized by continually reading out and concatenating the stored information

Information

Information in its most restricted technical sense is a message or collection of messages that consists of an ordered sequence of symbols, or it is the meaning that can be interpreted from such a message or collection of messages. Information can be recorded or transmitted. It can be recorded as...

 into a data stream

Data stream

In telecommunications and computing, a data stream is a sequence of digitally encoded coherent signals used to transmit or receive information that is in the process of being transmitted....

 to be converted into analog form.

The digital milliwatt is used in place of separate test equipment. It has the advantage of being tied in frequency and amplitude to the relatively stable digital clock signal

Clock signal

In electronics and especially synchronous digital circuits, a clock signal is a particular type of signal that oscillates between a high and a low state and is utilized like a metronome to coordinate actions of circuits...

 and power (voltage) supply, respectively, that are used by the digital channel bank

Channel bank

In telecommunications, a channel bank is a device that performs multiplexing or demultiplexing of a group of communications channels, such as analog or digital telephone lines, into one channel of higher bandwidth or higher digital bit rate, such as a DS-1 circuit.A channel bank may be located in...

.

Source: from Federal Standard 1037C

Federal Standard 1037C

Federal Standard 1037C, titled Telecommunications: Glossary of Telecommunication Terms is a United States Federal Standard, issued by the General Services Administration pursuant to the Federal Property and Administrative Services Act of 1949, as amended....

 and from the Code of Federal Regulations, Telecommunications

Code of Federal Regulations, Telecommunications

The Code of Federal Regulations, Telecommunications, containing the U.S. federal regulations for telecommunications can be found under Title 47 of the United States Code of Federal Regulations.-Commonly referenced parts:...

Parts 0-199 (edited for Wikipedia).

unsigned char ulaw_digital_milliwatt[8] =
{ 0x1e, 0x0b, 0x0b, 0x1e, 0x9e, 0x8b, 0x8b, 0x9e };