Line Path Switching Control Circuit - Toshiba GD-1210 Service Manual

4.2.2

Line path switching control circuit

NA/TW models
NCU board
C5 R4
RLY2
+12V
CML relay
1
1
4 Lb 9
0
Line
1
3 La 4
0
3 a2
External
telephone
4 b2
The line path switching control circuit consists of the CML relay (RLY2) and analog switch (IC51) on the
NCU board, the ASIC (IC29 [IC26]) on the FAX board and the other peripheral devices.
The CML relay is switched according to the CML1 signal output from the ASIC on the FAX board. When
the CML1 signal goes HIGH, Q51 comes on to turn ON the CML relay.
The analog switch is switched according to the CML1 signal and ATT3DB1 signal. When the CML1 sig-
nal or ATT3DB1 signal goes HIGH, the analog switch is turned ON.
Turning ON the CML relay and analog switch allow the MODEM to be connected to the line.
Signal Name Type
CML1 O
ATT3DB1 O
* Values in [ ] are for GD-1250/1270 in case that the descriptions vary between GD-1210 and GD-
1250/1270.
© 2006 - 2011 TOSHIBA TEC CORPORATION All rights reserved
Q51
R67
12 AG
8 T1
10
3
AG 3
IC53
R59
5
1
7
2
6
R66
13
R68
Ring signal
detection
circuit
Fig. 4-5
Active
H Line 1 CML Relay Control Signal
H Line 1 Attenuator Control Signal
4 - 5
08/04
3
6
R71
9,11
IC51
10
Analog
switch
IC53
1
4 1 2 1
0
IC52
1
15 6 7 2
0
1
14
0
Description
FAX board
3 CML1 21
IC29
[ IC26 ]
6 ATT3DB1 22
ASIC
1 TXOUT1 28,29
IC12
[ IC9 ]
2 RXIN1 32
MODEM
Destination
RLY2, IC51
IC51
GD-1210/1250/1270/1160/1260
ELECTRICAL CIRCUITS
4