3Com NBX 100 Administrator's Manual page 285

If the ACD has not reset since last system reboot, the system shows a null
reset date value.
Contention
The NBX system groups audio devices such as NBX Voicemail ports into a
pool or extension list in the dial plan. The NBX system uses this extension
list or pool for delayed announcements. The system selects an idle device
from this list in order to play a delayed announcement. The number of
devices in this pool is based on usage, and you can add or remove devices
in order to suit the call volume.
On a system with NBX Voice Messaging, this resource pool reserves the
NBX Voice Mail ports for Delayed Announcements and prevents them
from being used by Auto-Attendant or voice mail applications on the
system. This scheme helps the availability of voice mail ports for Delayed
Announcements.
On a busy system, there could be an additional delay in the playing of a
announcement. This condition can occur if all the audio resources (NBX
Voicemail ports) from the Delayed Announcement Audio Pool are in use.
If this delay occurs, the scheduled announcement must queue up for an
audio resource to become available before it can be played to the caller.
During that time, the caller either hears ring-back (when the NBX system
initially routes the call to the ACD Group for the initial announcement or
greeting) or Music-On-Hold (if the caller has already heard a
announcement, or the call is the result of a transfer or forward
operation).
To avoid this problem, you can:
Record or import announcements of short duration.
Add more audio resources (NBX Voicemail ports) to the Delayed
Announcement Resource Pool.
The system records contention instances and displays them on the
Statistics screen.
Using ACD 285