Oki B4100 - Manual (Page 450)

40055101TH Rev.4 450 /
D 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 of RI having the same frequency as incoming
RI.
E 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.
F Off-hook detectors (IC2, RL7)
These circuits detect the off-hook state of the telephone connected to the TEL1, TEL2,
through LINE terminal. 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.
G Impedance switches (CN15 to CN45)
These circuits set the impedance according to the line requirement.
220: 220 ohm + 820 ohm//115 nF (CN15)
275: 275 ohm + 850 ohm//150 nF (CN25)
370: 370 ohm + 620 ohm//310 nF (CN35)
600: 600 ohm (CN35)
H DC resistance switch (SW3)
This switch sets the DC resistance according to the line requirement.
I Ring impedance switches (S1-3 to S1-6)
These switches set the ring impedance according to the line requirement.
J Ring sensitivity switch (S4)
This switch sets the ring sensitivity according to the line requirement.
K Telephone cascade/parallel switches (S1-1 to S1-2)
To connect the telephone connected to the TEL1 terminal and an external telephone in
parallel, set the switches to ON.