scope:

This first part of EN 300 122 specifies the keypad protocol of the pan-European Integrated Services Digital Network (ISDN) as provided by European public telecommunications operators for the application to a range of supplementary services at the T reference point, or coincident S and T reference point (as defined in CCITT Recommendation I.411 [1]), by means of the Digital Subscriber Signalling System No. one (DSS1). The application of the present document to individual supplementary services is outside the scope of the present document. The keypad protocol provides a means of transferring keypad facility codes from the user to the network to control supplementary services and indicating network responses to the user. This protocol applies to supplementary service invocation in the user-to-network direction, and the keypad facility codes used for the invocation of individual supplementary services are network dependent. The protocol is stimulus in the sense that it does not require any knowledge about the invoked supplementary service by the user equipment. It is applicable to both the basic and primary rate access structures. Further parts of the present document may specify the method of testing required to identify conformance to the present document. The present document is applicable to equipment, supporting supplementary services using the keypad protocol, to be attached at either side of a T reference point or coincident S and T reference point when used as an access to the public ISDN.