The Base Station's Detector Circuit - Sanyo CLA-1380 Service Manual

CIRCUIT DESCRIPTION
1. THE BASE STATION'S DETECTOR CIRCUIT
(1) The ringing tone detector circuit
The ringing tone detect circuit detects the ring signal when the ringing tone is sent from the telephone line and in-
forms the IC401 micro processor that the signal has arrived.
The ring signal coming in from the telephone line is transmitted from telephone line @ to @. At this time IC903 switch
to "ON" and "OFF".
Then IC903 and Q909 control the level of pin 43 in
IC401. IC401
reads the time between " L" and "H" and thus deter-
mines that the ringing tone has been sent.
(The ringing tone is not detected if the voltage is less than 20 Vrms when received.)
TEL LINE@ -@+@-.@
INSTANT BREAK DOWN
RING SIGNAL
48V
I
TEL LINE
I I TEL LINE
I I
o-@
I I
@)to@
:+
IC401
PIN
43
~i k~~;t ,c401PIN43 ~ r: I
(2) The CPC (Calling Parity Control) detection circuit
This circuit detects the disconnect pulse (CPC), which is emitted from the telephone line when a caller hangs up while
CLA-1380AUS is in the AUTO answer mode, and inform pin 43 in IC401.
When the telephone line is closed (i, e. off-hook), the direct current from the telephone line flows from telephone line
@ to @. Then , IC901 switches to "ON" and pin 43 in IC401 get into "L".
If, at the time, the caller hangs
Up and the direct current in the telephone line is disconnected (through CPC), IC901
switches to "OFF". Pin 43
in IC401 then switches to "H".
CPC detection conditions
Detection begins 2.5 sec. following off-hook.
The CPC disconnect pulse is detected when pin 43 in IC401 is in the "H" level for 8 msec. or more.
IC902 . Q901 . Q902
BRANCH DETECT > IC401
PIN 44
RY901
T901
@— —
@
TEL SOCKET
LINE AMP
Q701 / Q702
IC901
* IC401
PIN 43
RING DETECT
IC903 . Q909
SWITCHING
~lC401 PIN 54
Q907
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