Meridian Nortel 1 Option 11C Technical Reference Manual page 433

Figure 56
Traditional OPS application configuration
NT1R20 Off Premise Station (OPS) analog line card
Note: OPS service should not be confused with off-premise extension
(OPS) service. OPS service is the provision of an extension to a main
subscriber loop bridged onto the loop at the serving CO or PBX.
Additionally, OPS as used to denote off-premise extension service
should not be confused with the OPS class-of-service assigned in the
Single-line Telephone Administration program (LD10).
Option 11C and 11C Mini
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