Kenwood TH-235A Service Manual page 12

TH-235A/E/234
CIRCUIT DESCRIPTION
@ Battery save circuit
The power circuit enters the battery save mode if no key off ratio of about 200 ms vs. about 800 ms (on/off ratio of
is pressed for 10 seconds or more while the squelch is about 200 ms vs. about 125 ms when the DTSS function and
switched in during reception state (SCAN OFF). paging function are turned on.) As the result, power con-
In the battery save mode, the output signal from the SAVE sumption in the standby state is reduced by controlling the
pin of the microprocessor turns Q211 on and off with the on/ 5C AVR consisting of Q210 which turns 5R on and off.
5C
Q212 Q210
5R t IC201
Q211
RB , SAVE SAC
s = 272
| ANy-
A
5MS
Fig. 12 Battery save circuit
® Remote control circuit
The remote control operation corresponding to the input remote control unit is pressed, this voltage is changed to the
digital voltage connected to the A/D pin, is performed by the voltage value divided by the resistor connected in series with
remote control circuit. the switch pressed and R226. The resultant voltage indicates
The voltage at the A/D pin is normally maintained to about which button is pressed.
5 V by means of R226. When the microphone button of the
5MS
Microprocessor ¥
16201
=
xl xl-x
r AFO sP z 3 7 = W
x AF AMP>—e eV, = x\
M oA] qin for] § y s ee
1 E - 5 ? B 9 °
R291 MIC
5MS We OF External
100 speaker
3.5
MIC AMP = o—A. ©
281 PTT
Microprocessor eG O 4
Perr
External
5MS + microphone
(*1) 4
10 uF (* 2)
*1 : Voltage appears from the internal 5MS line (5 V) via R291. It is
about 4.5 V when 5 mA flows.
"2: The capacitor is not necessary in the following cases: Make a
direct connection.
When ae capacitor to cut the DC voitage is connected to the exter-
nal device.
When a two-terminal capacitor microphone is used as the exter-
nai microphone.
Fig. 13 Speaker, microphone jack and remote control circuit
12