Xerox FaxCentre F110, Service Manual

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General Procedures / Information
6-84 12/04 FaxCentre F110
GP 37 RING
Incoming Ring
To signal the terminal equipment an incoming call during On-Hook, a defined AC signal is applied
by the PSTN network.
Figure 1
The level and the frequency as well as the on- off ratio (cadence) of the signal is within certain
limits Any change of the line voltage is detected by the ring detector which generates a pulse of a
defined duration. A changing line signal is mirrored by the ring detection signal (RING) with twice
the line signal frequency : f
ringer
= f
RING
/ 2. . An Incoming Ring on the line may be mirrored by the
loop detection signal. (INTLOOP) if LIU_HOOK=1.
On-Hook , Off-Hook Line Configuration
During terminal equipment On-Hook the line control signal is set inactive (HOOK = 0) to inhibit a
valid loop current. Due to the line voltage change, a change of the ring signal within the ring de-
tection HW-component may occur. If settled, only an idle loop current (On-Hook) is drawn from
the network.
Pulse-Dial (External Phone)
The line voltage and current change during external phone Pulse Dial has an effect for the ring
detection signal (RING) as long as the internal phone (HOOK = 0) stays On-Hook. The pulse di-
alling signals may generate some ring detection pulses !
Parallel Terminal Equipment Off-Hook (FCU On-Hook)
The loop current change due to an parallel off-hook condition has some effect for the idle loop cur-
rent (On-Hook state). A change of the line voltage may result in a short invalid change of the ring
signal !
Parallel Terminal Equipment Off-Hook (FCU Off-Hook)
Due to the possibility of connecting a parallel terminal equipment which, when also internal Off-
Hook, reduces the line voltage which may result only in a reduction of the loop current. This line
voltage change may also introduce an invalid ring detection pulse !
ringer
AC-signal
(line)
LIU_RING
EXTLOOP
T
ringer
T
RING =
T
ringer
/ 2
T
RING ON = 5ms
T
RING OFF =
T
RING -
T
RING ON