Oki OKIOFFICE 84 Service Manual page 423

8 SR (RL2)
This circuit connects the line with the telephone. During facsimile transmission, it discon-nects the telephone.
11 PP (RL6)
If this circuits detects MF or CNG tones without seizuring a line, it sets a proper receiving sensitivity.
12 DP (RL3)
This circuit generates pulse dials.
If the circuit detects MF or CNG tones without seizuring a line, it opens to increase the impedance.
13 Pickup RC (R5, C31)
These circuits insert a high-impedance resistor and capacitor serially to prevent the line impedance from dropping by
the line transformer T1.
14 Ring detectors (IC1)
These circuits detect a ring signal arriving to the line. If the input ring signal exceeds a specific voltage, the circuits
output a signal having of RI the same frequency as incoming RI.
15 Line transformer (T1)
This circuit processes send/receive signals required for facsimile transmission, dial tone receive signals required for
automatic dialing, and MF tone send and remote receive signals. It separates between the line and equipment in
terms of DC and also keeps a balance between the line and the ground. The transformer on the UNC board for
OKIFAX 5600 is covered with the shield case for the low-level receiving countermeasure.
16 Off-hook detector (IC2)
This circuit detects the off-hook state of the telephone connected to the TEL1, TEL2 through LINE terminals.
4.2 WN5 circuit diagram