This European Telecommunication Standard (ETS) addresses the network management messages and procedures across the A-bis interface, which is defined as Qx in GSM. The information model included here defines the objects and how they are addressed for purposes of operations and maintenance activities. There is a requirement for the A-bis interface to be open to allow interoperation between BTSs of different manufacturers working to the same BSC. This ETS addresses this requirement from O&M point of view, which allows this interworking to take place. It shows the split of NM functions between BSC and BTS. The procedures and coding of the messages are specified in detail. In practice, in addition to this ETS it is necessary that the content of manufacturer-dependent information fields be specified to fulfill the functionality. It is essential for operation that a BSC can handle the functions used by all its BTSs. Therefore, all items in this ETS are considered mandatory unless otherwise indicated in this ETS.