General Procedures / Information
FaxCentre F110 12/04 6-83
Figure 4
Incoming Ring
The line voltage change due to an Incoming Ring may have an effect for the external loop current
(EXTLOOP). During an incoming ring, while On-Hook, the ringer signal (see RING Signal Descrip-
tion) may be mirrored by the EXTLOOP signal !
Pulse-Dial (External Phone)
The line voltage and current change during external phone Pulse Dial has an effect for the external
loop current (EXTLOOP) as long as the internal phone (LIU_HOOK = 0) stays On-Hook. The
pulse dialing signals are mirrored by the EXTLOOP signal !
Parallel Terminal Equipment Off-Hook(On-Hook)
The line voltage change due to parallel Off-Hook has some effect on the internal loop detection
(EXTLOOP). If the parallel phone is Off-Hook in addition the loop current signal may be lost
(change) erroneously !
Table 1: External Phone Detection Table
LIU state LIU_HOOK PD EXT_LOOP Loop Current Ext. Phone
Onhook / No External
Phone
0 0 0 NO LOOP DET. NO EXT. PHONE
Onhook / External Phone 0 0 1 NO LOOP DET. EXT. PHONE
Offhook / External Phone 1 0 0 LOOP DET. No Change
Offhook / No External
Phone
1 0 0 LOOP DET. No Change
line
DC-voltage
- 40V
0V
+ 40V
LIU_RING
EXTLOOP
serial phone offhook serial phone onhook
External phone loop signalling
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