Oki B 4100 Maintenance Manual page 481

8) Return Loss Adjustment
The return loss adjustment is performed by the installed C-R networks corresponding to the
individual country. For adjusting the return loss, select the corresponding C-R network by
the designated DIP switch and adjust the return loss by changing the values of capacitors
and resistors.
The dip-switch set to ON corresponds to the country as shown in the table.
9) AGC (automatic gain control)
AGC is a function for adjusting the sending and receiving levels automatically in accor-
dance with the line current values, so that the optimal communication level is automatically
set. The circuit section to determine the AGC characteristics is formed by resistors R41
and R43 connected to the AGC terminal of the speech IC. The AGC gain is high when the
resistor values are small, and the AGC gain is low when the resistor values are large.
10) Pulse Dialling
Changing the make-and-break ratio is determined by the dip-switch SW4-1 and 2.
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11) MF dialling
The MF signal sending level is adjusted by the selection of resistors and capacitors
allocated for the individual countries by the dip-switch setting.
The dip-switch set to ON corresponds to the country as shown in the table below.
Increase the resistor value to lower the MF signal sending level, and decrease the resistor
value to raise the sending level. The difference between the high and low groups of the
MF signal is performed by changing the capacitance of the capacitor. The allowable level
difference between the high and low groups is (2 1) dB.
12) Manual Pad
The manual pad is used as a countermeasure by the ON setting of SW3-8 when howling is
occurs because of line conditions. (normally set to OFF)
40055101TH Rev.4
Country Dip-switch
UK SW1-5
Italy/Belgium SW1-6
Denmark SW1-7
Norway SW1-8
Setting SW4-1 to ON and SW4-2 to OFF corresponds to a 33% make ratio.
Setting SW4-1 to OFF and SW4-2 to ON corresponds to a 40% make ratio.
Country Dip-switch
UK SW2-1
Italy/Belgium SW2-2
Denmark SW2-3
Norway SW2-4
Symbol (network)
R29, C21, R26
R30, C22, R27
R31, C23, R28
R76, C54, R77
Symbol Rated Value
C31, R38 -9 dBm/-11 dBm
C70, R39 -6 dBm/-8 dBm
C71, R80 -9 dBm/-11 dBm
C72, R81 -9 dBm/-11 dBm
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