This standard addresses the code and format structures for both circuit connections as well as facility connections. Both of these connections are depicted through seven application specific combinations of data unit representation (four format structures). The seven format structures are: 1. message trunk circuits 2. message trunk groups 3. special services circuits 4. cable facilities 5. cable facilities with pair identification 6. carrier facilities 7. carrier facilities with channel identification Purpose Message trunk identification is used in any operation that requires unique identification of message trunks. It is used on circuit layout record cards and work order records in inventory and provisioning systems. Processes that key on message trunk identification include trunk forecasting@ provisioning and trunk servicing. Special services circuit identification is used in any operation that requires unique identification of special services circuits. It is used by special services administration@ provisioning@ design@ engineering@ planning and servicing. Facility identification is used in any operation that requires unique identification of facilities. It is used on network topology/architecture layouts@ disaster scenario planning and work order records in inventory and provisioning systems. Processes that key on facility identification include forecasting@ provisioning and service assurance.