Outline Of Parallel Pickup - Oki OF5700 Service Manual

2.9.2.6 Outline of Parallel Pickup

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.
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Why a PP function is needed !
As shown in the block diagram on the next page, telephone sets B, A, A' and A" are connected to a telephone line.
Since A, 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 16 in the block diagram.
However, off-hook status of telephone set B cannot be detected by the fax side.
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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 13. 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 the remote.
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Service Guide OKIFAX 5700/5900
Chapter 2 Installation
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