IS-728 specifies an Intersystem Link Protocol (ISLP) for circuit-mode data services.
These data services include Asynchronous Data (ADS) and Group-3 Fax as specified in
TIA/EIA/IS-99 and TIA/EIA/IS-135. The ISLP adapts between air-interface data rates and
higher-speed intersystem rates. The ISLP may be used between a serving system and an
anchor system, possibly through one or more tandem systems (see ANSI/TIA/EIA-41.1 for
details on "serving system", "anchor system", and "tandem system").