Lucent Technologies MERLIN LEGEND Release 5.0 Feature Reference page 217

MERLIN LEGEND Communications System Release 5.0
Feature Reference 555-650-110
Features
Digital Data Calls
Devices used for 2B data must be connected to MLX jacks that are programmed
as 2B data-capable. Devices that do not support 2B data should not be connected
to ports programmed for 2B data.
The MLX extension numbers used to add 2B data capability must correspond to
the adjunct extension number for the MLX telephone. By default in a 2-digit
numbering plan, these adjunct extensions are numbered beginning with the digit
7. If the MLX extension is 20, its corresponding adjunct extension is 720. In a
3-digit or Set Up Space numbering plan, the adjunct extension number is, by
default, the main extension number plus 200. (For details about numbering plans,
see ''System Renumbering'' on page
Once an MLX jack is correct programmed, a 2B data-capable device properly
connected to the jack should operate at the same data rate (up to 128 kbps) as an
NI-1 BRI line connected directly to a central office.
2B data calls are really two calls, one for each B-channel. (Similarly, ISDN
terminal adapters that connect to V.35 video systems must make and receive two
calls in order to provide double the speed of a single digital call.)
NOTE:
Users can use any combination of PRI, NI-1 BRI, and T1 to obtain a
2B data connection. However, data transfer speeds are slower on T1
Switched 56 lines (56 kbps on each line). Because of potential speed and
other conflicts, it is best to use the same type of facility for both the calls
that make up a 2B data call.
Considerations and Constraints
When a desktop video system is in passive-bus configuration (an MLX telephone
is connected to it), and the connected MLX telephone is using one of the
B-channels for any reason, the desktop video system can receive a call only as a
1B data call (some video systems do not support 1B data). This is called
B-channel contention and can cause problems with features that require two
B-channels, such as Voice Announce to Busy, Hold (including Hold for transfer or
conferencing), Call Waiting, and Automatic Callback.
Features that redirect calls (for example, Coverage, Forwarding, Data Hunt
Groups, and Night Service) can present problems for 2B data calls. For example,
a video system should not be a coverage sender because another video system
receiving calls for it can be assigned only one Cover button for the sending
extension. Therefore, only one call of a 2B data call is sent to the receiver, and the
second call continues to ring at the sending system.
See "Feature Interactions," later in this topic, for more information.
MLX modules of firmware vintage 29 are not compatible with 2B data. You must
program the feature on a jack whose module is of earlier or later vintage.
583.)
9
Issue 1
June 1997
Page 185