Oki OKIOFFICE84 Maintenance Manual page 306

UNC/WN5/FN5/DN5
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40672201TH Rev. 4
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.
Off-hook detectors (IC2, RL7)
These circuits detect the off-hook state of the telephone connected to the TEL1,
TEL2, through LINE terminals. IC2 uses a high detection sensitivity than of RL7. In
TEL/FAX mode, the higher sensitive IC2 is used to detect the off-hook state of the
telephone while the main equipment is hunting a line.
Usually, IC2 is short-circuited by the CML relay (7) in the standby state and RL7 is
used for off-hook detection.
Impedance switches (S5-1 to 5-2)
These circuits set the impedance according to the line requirement.
S5-1: 370 ohm + 620 ohm//310 nF (UK)
S5-2: 600 ohm (F)
DC resistance switches (CN26 and CN36)
These switches set the DC resistance according to the line requirement.
FICC (IC6)
This circuits reduces the DC resistance to increase the loop current momentarily to
assure operation of the switch at line seizuring.
Constant current circuits (Q1 and Q2)
These circuits provide DC characteristics according to the French line requirement.
Shunt (RL5)
This circuit prevents bell resonances in the telephone sets connected in parallel
during pulse dialing and also reduces distortions of the pulse waveform.
Communication line terminal switches (CN26 and CN36)
Unlike other countries, pines 2 and 5 are connected to the line for the UK commu-
nication line. Set the switches to "F" for France and "UK" for UK.
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