41309401TH Rev.4 364 /8.3 Outline of Parallel Pick UpParallel pick up is a function that controls a fax (to make a fax in receive mode) from a telephone setconnected parallel to a fax. The two possible parallel connections of telephone sets A and B are shownin the figure.ABTo modemLineSWFAXRemote controlAR1, AR2arrestersTELLINE 1DB1 IC2 IC3DP DCcircuitB RL343 MUTE09CML78SRIRing DetectorC5 R505C7 T1EImpedancematchingNT 5 G CN15 ~CN35ReceivingsensitivityAdjRL6ARRPSRIOH2IC1 DFIC5 OFF-HOOKDetectorQ1Cto ModemCN36MUTETEL CN1CN2Remote 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 telephoneline.Since A and A'' are connected to the line via fax, off-hook status of any of the telephone sets canbe detected by the OFF-HOOK Detector F in the block diagram. However, off-hook status oftelephone set B cannot be detected by the fax side.• PP ControlWhen a normal ring arrives at the fax from the line, the CML 7 turns on resulting in the formationof 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 orderto make the fax in the receive mode, then it becomes possible to detect the MF signals along thatroute.Block diagram for Parallel Pick Up Path.
