GSM Application Programming Interface
This European Telecommunication Standard (ETS) defines the GSM Application Programming Interface (GSM‑API) in two parts.
The first part describes, how compatibility to existing application interface ETS 300 838 [14] is covered for the GSM network. So existing PCI applications are able to be used in a GSM environment. For these applications the necessary mapping and local knowledge between application interface and network is described. The only modifications needed in ETS 300 838 [14] to fulfil this requirements are covered by changes of the parameter description. These changes of parameters are defined in clauses 4 and 5 of this ETS.
An application compliant with this ETS shall not imply compliance with ETS 300 838 (HPCI).
Clause 4 is meant to replace subclause 5.7 message parameters of ETS 300 838 [14]. which defines the parameters of the profile A of the HPCI.
NOTE 1:	Clause 4is for further study.
Clause 5 replaces subclause 6.8 parameter description of ETS 300 838, which defines the parameters of the profile B of the HPCI.
The second part defines GSM specific features. New GSM‑API applications need extensions to ETS 300 838 [14] which are defined in section  6 and 7of this ETS.
These sections are meant as an addition to ETS 300 838 [14]. They do not replace any clause of ETS 300 838 [14].
Clause  6 defines the extensions according to the profile A of ETS 300 838 [14].
NOTE 2:	Clause 6 is for further study.
Clause  7 defines the extensions according to the profile B of ETS 300 838 [14] (bit compatible to COMMON ISDN API).
The messages and the operating system dependent part of ETS 300 838 [14] will not be changed for GSM‑API.