AT&T Merlin II Release 3 System Manual page 12

BEHIND SWITCH
POOLED
2-4 Type of System
With this system type, the MERLIN II system operates behind a larger
telephone system such as a PBX. Each line appears on a separate button.
See Figure 2-4. The fixed feature buttons that appear on MERLIN II system
phones, including Conference, Transfer, Drop, and Hold, are controlled by
the larger system. See "Line Assignments in Behind-Switch Systems" in
Section 3, "Reference."
FIGURE 2-4 Example of a behind-switch system.
With this type of system, similar types of lines, such as WATS lines, are
grouped into line pools. See Figure 2-5. There are three types of pooled
systems and whenever you select any of these options, the system type is
automatically set to "pooled."
Button Access. You select a line pool by pressing its button.
Dial Access. You select a line pool by dialing its code.
Automatic Route Selection (ARS). The system places the call on the line
pool that has been identified as the most appropriate for that type of call.
See "Line Assignments in Pooled Systems" in Section 3, "Reference."
PBX
Line
Line
Line
A
B
C
MERLIN II
System Control Unit
Line
Line
Line
A
B
C