342-86400-445PS
Issue
4.0
October
2006
Page
68
Copyright
GE Multilin Inc. 2002
Splitting mode
disconnects the drop side of the circuit (upon
insertion of test jack) and allows tones to be injected and measured
for end-to-end or loopback testing.
Loopback
May be set for
None
(loopback off),
Local
or
Line (remote)
. The
loopback feature is used for test/maintenance purposes only.
In
Local
Loopback mode, the unit internally loops the VF signal
back to the VF interface at the digital side of the CODEC (Figure
12a). In this mode, a tone injected locally can be measured on the
unit's receive side.
In
Line (remote)
loopback mode, the unit internally loops the signal
back towards the far-end unit at the digital side of the CODEC.
This means that a signal transmitted from the far-end will be looped
back to the far-end. This allows to inject a tone from a VF Test Set
connected to the far-end unit and measure the tone received at the
far-end unit (Figure 12b). Note that if an external hybrid function
cannot be provided for testing, then an 86444 4W VF unit may be
used for testing purposes (Figure 12c).
RCV
XMT
2W FXS
4W VF
2W
4W
XMT
RCV
2W
VF
4W
VF
NEAR END
FAR END
A/D
D/A
D/A
A/D
(c)
RCV
XMT
2W FXS
2W FXO/FXS
2W
4W
XMT
RCV
4W
2W
2W
VF
2W
VF
NEAR END
FAR END
A/D
D/A
D/A
A/D
RCV
XMT
2W FXS
2W FXO/FXS
2W
4W
XMT
RCV
4W
2W
2W
VF
2W
VF
(a)
NEAR END
FAR END
(b)
D/A
A/D
A/D
D/A
RCV
XMT
2W FXS
4W VF
2W
4W
2W
4W
XMT
RCV
2W
VF
4W
VF
NEAR END
FAR END
A/D
D/A
D/A
A/D
(c)
RCV
XMT
2W FXS
2W FXO/FXS
2W
4W
2W
4W
XMT
RCV
4W
2W
4W
2W
2W
VF
2W
VF
NEAR END
FAR END
A/D
D/A
D/A
A/D
RCV
XMT
2W FXS
2W FXO/FXS
2W
4W
2W
4W
XMT
RCV
4W
2W
4W
2W
2W
VF
2W
VF
(a)
NEAR END
FAR END
(b)
D/A
A/D
A/D
D/A
Figure 12:
86445-32 2W FXS Unit Loopbacks: (a) Local
Loopback; (b) Line Loopback with 2W FXO or 2W FXS unit at far
end; (c) Line Loopback with 4W VF unit at far end