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CIRCUIT DESCRIPTION
2. INT/EXT Switching
There are two kinds of INT/EXT (universal connector)
switching:
1. Audio switching only (e.g. when the SP/MIC are
connected)
2. Switching of the ANT for SP/MIC and measure-
ment purposes
Identification between the two is done in the main MPU
IC1 (M37450E4FP).
* Audio switching only
Connecting the CON line at the universal connector
to GND causes the main MPU to switch the audio out-
put routing to the EXT port while SP: ON and IMS are
switched OFF.
TX RX UNIT
ANT
RF
12
Sw
4
6
* Switching of the ANT
Connecting the EDA line at the universal connector
to GND causes not only the audio but also the ANT is
to be routed to the EXT port by the main MPU.
When
the EDA
line is low, the PLS line is set high
resulting the ANT port is switched to EXT.
The MIC MUTE line is set true during the DTMF tones
are encoded, causing the MIC input is disabled to avoid
the speaker output signal is getting into the transmit
modulation.
UNIVERSAL
|
CONECTOR
EXT ANT
>|
(3
CONTROL
Ld
UNIT
|
PA
al
SP1
OF
05,6
|
E
SP
|
Emi
Sw
|
iNT
l
wic
1
SP
|
©
|swe
|
sP2
4
=e
)
~
¢
(e)
= O° 2
ma!
a
1)
-~O—
——|--|--—
--—=-|--|-—---|--|-
x a 0)
4d
PLS
PTT MON SPON con be
ob
5
4
MAIN p-COM
| o-leNO
|
CON
MICM
img CONT
LJ
O---O-~
Hi MIC
MIC
IMS
OF
MUTE
H! INT MICON
MIC
mC
sw
|
t
|
Q3
Q4
INT
SWB
~{
sw
mic
|
L
Fig. 10 INT/EXT switching
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