nMaintenance
 functions
 nsupervision of
 subscriber lines and trunk circuits
 nOperational
 functions
 nadministrative data as
 nsubscriber
 database
 nrouting
 database
 nstatistical data as
 nfrom where and whom
 subscribers call
 nholding times for
 different equipment types
 nutilization of IN
 services
 nUser services