Oki B4100 - Manual (Page 484)

40055101TH Rev.4 484 /
3-4 TEL-W2D circuit diagram
TEL-W2D board is for the Germany version only.
1) Speech IC
General functions of the speech IC are as follows:
•
Basic speech functions included.
• Separate receive pre-amplifier with signal output terminal
• Separate receive power amplifier input terminal, cause it is possible to mixing input.
• Balanced input for microphone input to provide immunity to common mode noise.
• MF pre-amplifier input terminal is possible to mixing input.
• Dial pulse waveform improvement circuit included.
• Manual pad function included.
• The transmit, receive, and DTMF amplifiers are provided with AGC in accodance with
the line circuit.
2) Sending Level Adjustment
The sending level can be adjusted by resistor R55 connected in parallel with the section in
front of the transmitter. Increase the resistor value to lower the sending level, and decrease
the value to raise the level.
3) Receiving Level Adjustment
The receiving level is determined by the resistor value of R35. Decrease the resistor value
of R35 to lower the receiving level, and increase it to raise the level.
4) Frequency Response Adjustment
The high range frequency response of the transmitter is determined by the capacitance of
C61. Increase the capacitance of C61 to lower the high range level, and decrease the
capacitance to raise the high range level. The low range frequency response is determined
by the capacitance of C36 and C37. Increase the capacitance of those capacitors to raise
the low range level, and decrease the capacitance to lower the level. When the capacitance
of C36 and C37 are changed, both capacitors should have the same value.
The high range frequency response of the receiver is determined by the capacitance of C29.
Increase the capacitance of C29 to lower the high range level, and lower the capacitance to
raise the level. The low-range frequency response is determined by the capacitance of C26.
Increase the capacitance to raise the low-range level, and lower the capacitance to decrease
the low-range level.
5) Side-Tone Adjustment
The side-tone level is determined by the values of R19, R22 and C16.
Note: Changing the side tone level setting affects the sending and receiving levels, the
verification and readjustment of the sending and receiving levels, and the verifica-
tion and the readjustment of the side tone level are required.
6) DC V-I (voltage-versus-current) Characteristics Adjustment
The DC V-I characteristics can be changed by mounting or not mounting D10 and D11.
When D10 and D11 are mounted the DC V/I value is raised. When these diodes are deleted
the DC V/I value is lowered. R202 is a 0
Ω
resistor, which is mounted when D10 and D11
are not being installed.