digital telephony Telephony ( ) is the field of technology involving the development, application, and deployment of telecommunications services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is ...

, the digital milliwatt is a standard test signal that serves as a reference for analog signal levels in the telecommunications network.Anttalainen T., ''Introduction to Telecommunications Network Engineering'', Artech House (2003). When decoding the digital milliwatt, a

PCM Pulse-code modulation (PCM) is a method used to Digital signal (signal processing), digitally represent analog signals. It is the standard form of digital audio in computers, compact discs, digital telephony and other digital audio application ...

decoder produces a sinusoidal signal with a

frequency Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...

of with one

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 in honor o ...

power Power may refer to: Common meanings * Power (physics), meaning "rate of doing work" ** Engine power, the power put out by an engine ** Electric power, a type of energy * Power (social and political), the ability to influence people or events Math ...

(, a reference for

dBm0 dBm0 is an abbreviation for the power in decibel-milliwatts (dBm) measured at a zero transmission level point (ZLP). dBm0 is a concept used (amongst other areas) in audio/telephony processing since it allows a smooth integration of analog and di ...

). The digital milliwatt signal is encoded by eight 8-

bit The bit is the most basic unit of information in computing and digital communication. The name is a portmanteau of binary digit. The bit represents a logical state with one of two possible values. These values are most commonly represented as ...

words corresponding to one pulse-code modulated cycle of the signal, sampled 8000 times per second. It is typically stored in

read-only memory Read-only memory (ROM) is a type of non-volatile memory used in computers and other electronic devices. Data stored in ROM cannot be electronically modified after the manufacture of the memory device. Read-only memory is useful for storing sof ...

(ROM) in the telecommunication equipment.AT&T, ''Digital Channel Bank Requirements And Objectives'', Publication No. 43801 (December 1978). page A6. The digital milliwatt signal is often generated in instruments in place of separate test equipment. It has the advantage of being tied in frequency and amplitude to the relatively stable digital

clock signal In electronics and especially synchronous digital circuits, a clock signal (historically also known as ''logic beat'') is an electronic logic signal (voltage or current) which oscillates between a high and a low state at a constant frequency and ...

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

channel bank In telecommunications, a channel bank is a device that performs multiplexing or demultiplexing ("demux") of a group of communications channels, such as analog or digital telephone lines, into one channel of higher bandwidth or higher digital bit ...

References

{{FS1037C Telephony signals