Outline Of Parallel Pick Up - Oki OKIFAX4550 Maintenance Manual

8.3

Outline of Parallel Pick Up

Parallel pick up is a function that controls a fax (to make a fax in receive mode) from a telephone set
connected parallel to a fax. The two possible parallel connections of telephone sets A and B are shown
in the figure.
Remote control: To control a fax from telephone set A.
Parallel Pick UP (PP): To control a fax from telephone set B.
• Why a PP function is needed!
As shown in the following block diagram, telephone sets B, A and A'' are connected to a telephone
line.
Since A and A'' are connected to the line via fax, off-hook status of any of the telephone sets can
be detected by the OFF-HOOK Detector F in the block diagram. However, off-hook status of
telephone set B cannot be detected by the fax side.
• PP Control
When a normal ring arrives at the fax from the line, the CML 7 turns on resulting in the formation
of an AC loop via circuit C. The AC loop makes it possible for the modem to detect the AC signals.
If a user hooks up telephone set B after the first ring and enters the MF 2-digit special code in order
to make the fax in the receive mode, then it becomes possible to detect the MF signals along that
route.
CN2
TEL
SR
8
7
TEL CN1
CML
1
LINE
AR1, AR2
arresters
Block diagram for Parallel Pick Up Path.
41309401TH Rev.4
Remote control
A
Line
B
OFF-HOOK
IC5
F
Detector
IC1 D
I
Ring Detector
C
C5 R505
B RL3
MUTE
9
DB1 IC2
3
DP
DC
circuit
4
Q1
FAX
To modem
SW
Impedance
matching
E
NT 5
T1
C7
IC3
A
RL6
0
MUTE
CN3
OH2
RI
G CN15 ~
CN35
S
6
to Modem
Receiving
RP
sensitivity
Adj
R
364 /