Oki OKIFAX 5400 Maintenance Manual page 330

3-2 TEL-W2 circuit diagram
Note: Refer to each country's hardware parameters comparison table.
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 amplifier are provided with AGC in accordance
2) Sending Level Adjustment
The sending level is determined by the circuit section formed by resistors R55, R56,
R57 and R58, and the bits of SW3 connect the resistors in parallel. The sending level
is maximum when all the bits of SW3 are set to ON, and minimum when all the bits
of SW3 are set to OFF.
3) Receiving Level Adjustment
The receiving level is determined by the circuit section formed by resistors R34, R35,
R36, R82, R83 and R84, and the bits of SW5. The receiving level is minimum when
all the bits of SW5 are set to ON, and maximum when all the bits of SW5 are set to OFF.
4) Sending Frequency Response Adjustment
The circuit section affecting the low range level of the sending frequency response is
formed by capacitors C59, C35, C36 and C60, which are connected in series to the
section in front of a transmitter. The low range level can be adjusted by the ON/OFF
setting of bits 1 and 2 of SW3. The high range level can be adjusted by the ON/OFF
setting of SW6-5.
Note: When the frequency response is changed, the sending and receiving levels
5) Side Tone Adjustment
The setting of the side-tone level is performed by the setting of SW1-1 through 8 and
SW2-1. One of these bits it set to ON for each individual country. The side-tone level
is interrelated with the receiving and sending level. The side-tone level becomes
higher when the sending and receiving level are set lower.
Note: After the side tone level is changed, the sending and receiving levels change,
6) DC V-I (voltage-versus-current) Characteristics Adjustment
The adjustment of the DC V-I characteristics at the time of line supplement is
performed by D10, D11, D12, SW2-7, R25 and SW2-8. When raising the DC V-I value,
set SW 2-7 to OFF or SW2-8 to ON. When decreasing the value, set SW2-7 to ON,
or SW2-8 to OFF.
40838301TH Rev.1
with the line current.
may be changed. Verify the sending and receiving levels after adjustment.
so readjust the sending and receiving level and reverify and readjust the side
tone.
TELU/TEL-W2/TEL-W1/TEL-W2D/TEL-W2F
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