BCP 47 Language Tags (The Internet Best Current Practices (BCP) for language tags).
A language tag is composed of a sequence of one or more subtags such as language, region, variant and script subtags.
When a language tag is comprised of more than one subtag, the subtag values are separated by the "-" character.
You will most commonly find language tags written with 2 subtags - language and region. For example: en-US.
retry_intervalinteger
Retry originator minutes.
The amount of time to wait before re-trying a busy automatic callback originator.
retry_total_timeinteger
Monitor Minutes.
The amount of time to camp-out on the busy line, waiting for it to become idle.