<communications> (Digital Signal or Data Service level)
Originally an AT&T classification of transmitting one or
more voice conversations in one digital data stream. The best
known DS levels are DS0 (a single conversation), DS1 (24
conversations multiplexed), DS1C, DS2, and DS3.
By extension, the DS level can refer to the raw data rate
necessary for transmission:
(where K and M signify multiplication by 1000 and 1000000,
rather than powers of two). In this sense it can be used to
measure of data service rates classifying the user access
rates for various point-to-point WAN technologies or
standards (e.g. X.25, SMDS, ISDN, ATM, PDH).
Japan uses the US standards for DS0 through DS2 but Japanese
DS5 has roughly the circuit capacity of US DS4, while the
European standards are rather different (see E1). In
the US all of the transmission rates are integral multiples of
8000 bits per second but rates above DS1 are not necessarily
integral multiples of 1,544 kb/s.
