Using “D” Messages for Layer 3 • 8-7 •
The H.110 Basic Rate ISDN Board
7F Interworking, unspecified
8.3.3 Directory Numbers
The called or calling numbers in “D” messages are represent by the string
of digits. Additional information that is encoded into the information
element such as the type of number or numbering plan are added by the
firmware based on the context and length. For NT ports, presentation of
calling numbers is always allowed as the application has control of
presenting this number. If the default called number is used, it is
considered part of a Local ISDN numbering plan. For TE ports, the
numbering plan of the called number is based on the length, with numbers
shorter than 7 digits being considered private plans, 7 digit numbers local,
10 digit numbers national and longer numbers international.
8.3.4 Feature Keys & Indication Status
Feature Keys are keys on a station set that can be used to signal the
network that a specific feature should be implemented. Feature codes
range from 0 to 63 and are encoded as two hexadecimal digits in “DF”
messages. The exact meaning of a feature key code is dependent both on
context and on the particular piece of network equipment involved.
Feature Indicators are lights or other indicators on ISDN Station sets.
These can be used for a variety of purposes such as indicating a feature
such as conferencing is in use or that messages are waiting. The encoding
of the meaning of a particular feature is both hardware dependent and
system dependent, that is the same code may represent different things on
different station sets. However, the status of the indicator is restricted to
four choices. These are:
I Idle or off
A Active or on constantly
Q Prompt, a fast blink
P Pending, a slow blink
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