|  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  |  | 
   
    | n | Different alarm
    classes 
 |  | 
   
    | n | Vital functions
    and circuits 
 |  | 
   
    |  | (as SS7 and group switch) 
 |  | 
   
    |  | use secured
    paths and 
 |  | 
   
    |  | backups 
 |  | 
   
    |  | Procedures
    provided for: 
 |  | 
   
    |  | 
   
    |  | n | troubleshooting 
 |  | 
   
    |  | n | fault
    diagnostics 
 |  | 
   
    |  | 
   
    |  | n | hardware faults
    can 
 |  | 
   
    |  | be isolated 
 |  | 
   
    | n | Supervision is
    realized also 
 |  | 
   
    |  | by connecting
    maintenance 
 |  | 
   
    |  | units to the
    network 
 |  | 
   
    | n | Important
    switches have 
 |  | 
   
    |  | extensive
    backup equipment 
 |