AT&T MERLIN LEGEND Release 4.0 Feature Reference page 121

Feature Reference
In the limited Centrex configuration, some telephones may have prime lines
while other telephones access the prime lines through a pool. Telephones can
also be assigned ground-start, tie, or DID lines, which is not possible in full
Centrex. Telephones without prime lines can use a Pool button to access
Centrex facilities or may use an SA button to access pooled facilities by dialing
an access code. Once connected to a pool, users may dial other Centrex
extensions or dial an access code for outside calls. Outside calls made by
using an SA button to access a pool require two access codes for outside calls,
one for the pool and one for outside lines on Centrex.
For limited Centrex operation, the communications system must be in Key or
Hybrid/PBX mode. The total system operates on three levels, as shown in
Figure 5. The telephone user must be aware of which level he or she is at when
making a call or activating a feature.
Central Office Central Office
(External Calls) (External Calls)
MERLIN LEGEND
Communication Systems
• 2, 3, or 4-digit Numbering Plan
• Hybrid/PBX mode features
Figure 5. Limited Centrex Service
Differences Between Full and Limited Centrex
The major difference between full Centrex and limited Centrex is where and how
PBX functions are provided:
Centrex Service Centrex Service
• 4-digit Centrex calls • 4-digit Centrex calls
• Use of Centrex Features • Use of Centrex Features
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Centrex Operation