The canonical form of a fax number is the fully qualified number that uniquely identifies the destination. The Canonical Form is a field in the Dialing Rules database.
Typically, a canonical form can be specified
by providing both the country and area code of the fax number. Thus, the
1 604 555 1212 is the Canonical Form of the local call
The use of the Canonical Form is in batching of faxes. If two faxes are using
a Class or Classes that allow batching, and the Canonical Form of the two faxes
are the same, they would be batched together and sent in one call. This can
reduce costs because many long distance carriers charge extra
for the initial one minute or so.
Also the time spent during the start of the call to initialize the fax
machine is incurred only once.