Oki OKIOFFICE44 Service Manual page 270

A3.1.6 R44 Circuit Diagram
1. Block diagram
The circuit diagram consists of Modem (14.4 kbps).
Modem consists the following functions:
• Modulation/demodulation
Modulation type:
1)
2)
3)
4)
• Automatic adaptive equalizer for G3 receive data with 300 bps data excluded.
• Generation of signal tones
• PB tone (multi-frequency tone) generation
• Detection of single tones
• D/A converter for send data (TX)
• A/D converter for receive data (RX)
• Amplitude equalizer for RX
• Selectable attenuation for TX
• Automatic gain control
Figure A3.1.6 shows the related signals of Modem.
IC8
29.4912 MHz
X'tal
Modem
14.4 kbps
Board Descriptions
ITU-T Rec. V17 (14400/12000/9600/7200 bps) for G3 picture data.
ITU-T Rec. V29 (9600/7200 bps) for G3 picture data.
ITU-T Rec. V27 ter (4800/2400 bps) for G3 picture data.
ITU-T Rec. V21 channel 2 (300 bps) for binary signals defined in ITU-T Rec. T.30.
AD0 to AD7
A1 to A7
MDINT1-N
MDRST-N
MDCSI-N
MDMRD-N
MDMWR-N
IC12
7
IC12
Figure A3.1.6 Related Signals of Modem
A - 28
R44
CPU
IC2
IOGA
S
R
RP
OKIOFFICE 44 Serv. Man., P/N 59276801
NCU
CN10 CN3
A8, B8 S
A6, B6
R