Toshiba ESTUDIO170F, Руководство по обслуживанию

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January 2005 © TOSHIBA TEC e-STUDIO170F Circuit Description
7 - 67
7.4.7 External TEL Control Circuit (EU/AU models only)
Fig.7-49
The external TEL control circuit consists of the transformer (T2), relay (RLY5) and photo-coupler (PC4),
the ASIC (I/O port: IC38) on the main PBA, and its peripheral devices. It outputs a ring signal to the
external telephone and detects the hook status of the external telephone connected to CN3 or CN5.
When the EXTTEL signal output from the ASIC goes HIGH, Q12 turns on and +12V is applied to RLY5
to turn it on. This allows the external TEL control circuit to be connected to the external telephone for
each control described below.
Upon receiving a CI signal, the ASIC outputs the RGCLK signal as a pulse signal to turn on and off Q13
and Q14. This 24V to be supplied or cut off to the coil in the primary circuit of T2 and a call sig-
nal to be output from the secondary circuit to the external telephone. Then it causes the external tele-
phone to ring.
When the handset of the external telephone has been lifted, current flows through the line to turn on
PC4. This causes the EXTHOOK signal to go LOW and input to the ASIC to detect that the handset of
the external telephone is lifted.
Signal Name Type Active Description Destination
EXTTEL O H External TEL relay control signal Q12
EXTHOOK I L External TEL hook detect signal ASIC
RGCLK O - External TEL ring generate signal Q14
T2
CML
EXTTEL
3
5
AG
Q4
CN3
Lb
La
0
1
0
1
3
10
12
4
9
1
10
3
5
4
3
2
1
8
12
9
4
1
+12V
RLY3
CML relay
4
3
a2
b2
2
5
CN5
a2
b2
3
4
3
5
49
53
Main PBA NCU PBA
IC38
ASIC
(I/O port)
Ring signal
detection
circuit
SG
PG
Q13
RGCLK
9
Q14
9 58
EXTHOOK
22 22 39
+24V
+5V
R54
R53
D6
C41
0
1
0
1
+12V
RLY5
Relay
AG
Q12
R55
PC4
CN4
CN16
External
TEL
Line