D176 Files are used to transfer information regarding Method 1 collect calls from the connecting administration to the billing administration. Full details of the composition of D176 files may be obtained from ITU (a fee may be levied).
A very brief look at how D176 files are transmitted and processed can be seen in the Collect Call Connections presentation.
This page will outline the concepts of D176, but will not go into details.
The files are built at regular intervals - the interval and size of each file depending on several factors, including:
- Number of records generated per day for each administration
- Agreements between the administrations
Each file contains at least one, possibly several, batches of call data, with each batch consisting of three parts:
A batch contains at least one call record, with the maximum by agreement between the administrations - usually 100, 1000 or 2000 records.
In the examples that follow the telephone numbers used have been deliberately chosen to be invalid - both United Kingdom and France use 10 digit numbers.
The Batch Header comprises an identifier (HDR), batch number, sending and receiving administration codes, and the date the batch was created.
is the header for batch 123 from United Kingdom (44) to France (33) created on September 23.
Note that there is no indication of the year in the date.
Each call record contains sufficient information for billing the call - time and date of connection, call duration, called (=billed) number, calling number.
The record may also contain additional information regarding any facilities used in connecting the call, for example: person-to-person.
209205551234 3142345 11012
is a call record for a person-to-person call connected on September 20 for 12 minutes, from a payphone 5551234 to 3142345.
The Batch Trailer is similar to the Header, but also includes checks used to ensure the batch has not been corrupted in transmission. These checks are the total records in the batch, plus the total duration of the calls.
TRL12344 092333 0000040000044
is the trailer record for batch 123 from United Kingdom to France created on September 23. The batch contains 4 records with a total duration of 44 minutes.
A complete batch of data from United Kingdom to France may resemble: