2-6
Cisco ONS SONET TL1 Command Guide, R6.0
Chapter 2 Procedures and Provisioning
2.2.1 Test Access Terminology
unit (RTU) also provide the capability of splitting a circuit under test. A split consists of breaking the
transmission path of the circuit under test. This is done out of service. The two sides of the access point
are called the Equipment (E) and Facility (F) directions. For a 4-wire or 6-wire circuit, the transmission
pairs within the access point are defined as the A and B pairs. The circuit under test should be wired into
the access point so the direction of transmission on the A pair is from E to F, and the transmission
direction for the B pair is from F to E (Figure 2-1).
Figure 2-1 Circuit With No Access Dual FAD TAP
A dual FAD (facility access digroup) TAP uses twice the bandwidth of the circuit under test. This can
be specified by the TAPTYPE parameter as shown in ED-<MOD2> command syntax in the “2.2.2 TAP
Creation and Deletion” section on page 2-7. The values are SINGLE/DUAL. It defaults to DUAL.
A single FAD TAP uses half the bandwidth as that of the dual FAD, for example, it will use the same
bandwidth as the circuit accessed for the TAP creation. This can be specified by the TAPTYPE parameter
as shown in the “2.2.2 TAP Creation and Deletion” section on page 2-7. The values are SINGLE/DUAL.
The MONEF, SPLTAB and SPLTEF modes are not supported by single FAD TAPs (Figure 2-2).
Figure 2-2 Circuit With No Access Single FAD TAP
2.2.1 Test Access Terminology
BRTU—Broadband remote test unit
DFAD—Dual facility access digroup
FAD—Facility access digroup
FAP—Facility access path
LOOPE—Split/loop access on A and B paths equipment side
LOOPF—Split/loop access on A and B paths facility side
MONE—Monitor access with signal detector on A path
61106
A
E
B
F
"Mapped"
AID
AID
Dual-FAD TAP
(2 times the bandwidth
of the circuit accessed)
102052
A
E
B
F
"Mapped"
AID
AID
Single FAD TAP
(same bandwidth
as circuit accessed)
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