# Digital milliwatt

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Code sequence of the digital milliwatt in μ-law and A-law encodings.[1] Word number Hexadecimal code μ-law A-law 1 1e 34 2 0b 21 3 0b 21 4 1e 34 5 9e b4 6 8b a1 7 8b a1 8 9e b4

In [digital telephony](/source/Digital_telephony), the **digital milliwatt** is a [standard test signal](/source/Standard_test_signal) that serves as a reference for analog signal levels in the telecommunications network.[2] When decoding the digital milliwatt, a [PCM](/source/PCM) decoder produces a sinusoidal signal with a [frequency](/source/Frequency) of 1 kHz with one [milliwatt](/source/Milliwatt) in [power](/source/Power_(physics)) (0 dBm, a reference for [dBm0](/source/DBm0)).

The digital milliwatt signal is encoded by eight 8-[bit](/source/Bit) words corresponding to one pulse-code modulated cycle of the signal, sampled 8000 times per second. It is typically stored in [read-only memory](/source/Read-only_memory) (ROM) in the telecommunication equipment.[1]

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](/source/Clock_signal) and power (voltage) supply, respectively, that are used by the digital [channel bank](/source/Channel_bank).

## References

1. AT&T, *Digital Channel Bank Requirements And Objectives*, Publication No. 43801 (December 1978). page A6.

1. Anttalainen T., *Introduction to Telecommunications Network Engineering*, Artech House (2003).

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Adapted from the Wikipedia article [Digital milliwatt](https://en.wikipedia.org/wiki/Digital_milliwatt) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Digital_milliwatt?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.