Xerox FaxCentre F110, Service Manual

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General Procedures / Information
FaxCentre F110 12/04 6-81
GP 36 EXTLOOP Signal
During FCU Off-Hook, the terminal equipment is connected to the line, and the external phone
completely disconnected, so no external phone detection is possible.
During terminal equipment On-Hook (HOOK = 0, PD = 0), the external terminal equipment is con-
nected to the line by LA2, LB2. If the external terminal equipment goes Off-Hook (e.g. by lifting the
Handset) it draws a loop current from the network (I
Ext_Loop
). This current change is sensed by
the Loop Detection Component and a status (EXTLOOP) signal is activated as long as the exter-
nal equipment is Off-Hook and the internal is disconnected
Figure 1
If the external terminal equipment is connected with the line (HOOK = 0, PD = 0) (going Off-Hook),
a valid loop current has to be drawn to established a valid connection.
Figure 2
PSTN
Network
LA
LB
U
Line
I
Line
LB2 LA2
I
Int Loop
I
Ext Loop
LIU_HOOK
Terminal
Equipment
PD
0
0
1
External phone On Hook
Loop Current
[mA]
Valid External Loop Current
No External Loop
External Loop
Current settling
min. Loop Current
threshold
Idle Loop Current
External Off-Hook External On-Hook
EXTLOOP