AT&T MERLIN LEGEND System Reference Manual page 490

Functional Description
FCC Registration
KF Classification
MF Classification
Behind Switch
Considerations
The FCC has no Behind Switch classification, so the system is registered under
the FCC category it parallels-either KF (a Key system) or MF (a hybrid system).
The AT&T account representative or authorized dealer who planned the
system's mode of operation provides the FCC registration number that the
customer reports to the local telephone company. This number includes the
letters "KF" or "MF" The guidelines used to determine the system's classification
are as follows.
The system is registered under the KF classification in each of the following
cases:
No outside lines are connected directly to the control unit (all outside lines
feed the host system's main switch, and the system accesses that switch's
pool).
Outside lines are connected directly into the control unit and are assigned to
buttons on one or more telephones.
Outside lines are connected directly to the control unit, and none of these
lines is a ground-start line.
No pooled trunks are used.
Systems that qualify as Behind Switch mode for the FCC are modified during
installation to set the "KF option" (or "strap"), which prohibits the assignment of
ground-start lines. The FCC registration number for this type of system is
AS593M-72914-KF-E.
The system is registered under the MF classification if all outside lines
connected directly to the control unit are ground-start lines.
The processor module in systems that qualify as Key mode for the FCC must be
modified during installation to set the "KF option," which prohibits the
assignment of ground-start lines. The FCC registration number for this type of
system is AS593M-72682-MF-E.
Operating the system in the Behind Switch mode is appropriate for users who
are part of a large organization. For example, a department might not want (or
be able) to support a large-capacity PBX. Piggy-backing the system behind the
host switch, however, gives the advantage of the host's features and functions.
Single-line telephones can be setup in two ways in Behind Switch mode. In the
first way, the user has constant access to the Prime Line but cannot make
intercom calls or use system features. In the second way, the user can make
and receive intercom and Prime Line calls and can use system features, but the
user must dial a dial-out code to make an outside call.
Businesses served by Centrex that have many locations can have the individual
locations connected in Behind Switch mode to the Centrex.
Modes of Operation 4-21