External Tel Control Circuit (Eu/Au Models Only) - Toshiba e-STUDIO170F Service Manual

7.4.7

External TEL Control Circuit (EU/AU models only)

NCU PBA
+12V
CML relay
1
Lb
4 4
Line
La
3 9
a2
2
+12V
b2
5
1
External
TEL
a2
3 9
b2
4 4
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 causes +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
EXTTEL O
EXTHOOK I
RGCLK O
January 2005 © TOSHIBA TEC
RLY3
12
1
0 3
1
0 10
RLY5
Relay
12
D6
R53
1 8
0 10
R54 C41
1 5
0 3
+5V
R55
2 4
PC4
1 3
SG
Fig.7-49
Active Description
H External TEL relay control signal
L External TEL hook detect signal
- External TEL ring generate signal
7 - 67
Main PBA
3 3
Q4
AG
5 5
Q12
AG
+24V
T2
9 9
Q14
Q13
PG
22 22
Ring signal
detection
circuit
Q12
ASIC
Q14
e-STUDIO170F Circuit Description
CML
49
EXTTEL
53
IC38
ASIC
( I/O port )
RGCLK
58
EXTHOOK
39
Destination
7