"These standards detail definitions@ methods of measurement@ and minimum performance characteristics of 800-MHz cellular subscriber units. These standards share the purpose of the Mobile Station - Land Station Compatibility Standard for Dual-Mode Narrowband Analog Cellular Technology (i.e. the ""compatibility specification"" and subsequent revisions thereof) of assuring that a subscriber unit can obtain service in any cellular system that meets the compatibility requirements of the compatibility specification. Compatibility@ as used in connection with these standards and the compatibility specification@ is understood to mean: Any subscriber unit is able to place and receive calls in any cellular system. Conversely@ all cellular systems are able to place and receive calls with any subscriber unit. To assure compatibility@ it is essential that both radio system parameters and call processing parameters be specified. The speech filtering@ modulation@ and RFemission parameters commonly encountered in two-way radio systems have been updated and expanded to reflect the unique radio plan upon which cellular systems are based. The sequence of call processing steps that the mobile and land stations execute to establish calls has been specified in the compatibility specification along with the digital control messages and analog signals that are exchanged between the two stations. A subscriber unit is intended to be used while in motion or during halts at unspecified points. It is assumed that subscriber units include portable units (e.g.@ hand-held ""personal"" units) as well as units installed in vehicles. Although the basic purpose of cellular telecommunications has been voice communication@ evolving usages (e.g.@ data) may allow the omission of some of the features specified herein provided that the system compatibility is not compromised. These standards concentrate specifically on the Subscriber Unit; they cover the operation of the land station@ the cellular switch@ and the cell control equipment only to the extent that compatibility with the compatibility specification is assured."