Canon FAX L1000 Service Manual page 515

3.6.4 G4 board components
Slave CPU
V.853 A
SRAM
(IC21)
256Kbit
SRAM
Main CPU
FUNK
16Kbit
V.821
(IC20)
X2
(IC8)
(IC48,49)
Audio IC (IC45)
MODEM
Port
R288F
SW
(IC67)
Parallel/
Serial
Audio IC (IC46)
Conversion
(IC10)
MODEM
Port
R288F
SW
(IC52)
a) DTMF signal detection circuit
This circuit uses a dedicated IC (IC38 DTMF receiver) to detect a DTMF signal.
b) ISDN interfade IC (IC24)
This YAMAHA-made IC YM7405C has Layer 1 functions, Layer 2 functions(LAPD), and
Layer 3 interface functions for connection to an ISDN circuit.
c) PCM CODEC IC (IC51, IC69)
The PCM CODEC IC, OKI-made MSK7578VMS-K, converts analog audio signals output
from a G3 modem to PCM digital signals to implement G3 transmission through ISDN
lines. This IC converts PCM digital signals to analog audio signals.
d) Modem IC (IC52, IC67)
The modem IC, CONEXANT R288F, G3-modulates transmit data received from a CPU
according to ITU-T V.17, V.21, V.27ter, V.29, and V.34 in transmit mode. This IC G3-
demodulates the signal received through the line according to ITU-T V.17, V.21, V.27ter,
V.29, and V.34 in receive mode. The IC detects a DTMF signal through ISDN lines.
TWINS
(IC39)
ROM DRAM
8Mbit 8Mbit
(IC1) (IC41)
PCM
CODEC
(IC51)
Port
SW
PCM
CODEC
(IC69)
Fig. 5-73 Component bloock diagram
5-157
FAX-L1000 Chapter 5: Appendix
+5/+12/+24V
-12V
T1
ISDN
I/F
T2
(IC24)
DTMF Receiver
(IC38)
PCM
Analog
CODEC
Port I/F
(IC50)
Speaker
Speaker
Driver
PSU
TWINS SCNT
+5V
G4
Relay
PC/DC
ISDN LINE
JACK
Not mount