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TK-3170
5-3. Low Battery Warning
The battery voltage is monitored by the microprocessor
(IC7 pin 123 : BATTLVL). When the battery voltage falls be-
low the voltage set by the Low Battery Warning adjustment
during the transmission, the red LED blinks to notify the op-
erator that it is time to replace the battery (When the "On
TX" option (default setting) under the Battery Warning / sta-
tus function in the FPU is selected.). If the battery voltage
falls below 5.9V, the transceiver does not transmit and the
warning tone beeps while the PTT switch is pressed.
Low battery warning
The red LED blinks during
the transmission.
The red LED blinks and
the warning tone beeps while
the PTT switch is pressed.
R27
SB
Fig. 10 Low battery warning
5-4. Battery Type Detection
The transceiver automatically detects the battery type,
measuring the resistance between the S-terminal and + ter-
minal on the battery pack and changes the supplied voltage
to the S-terminal as below. The microprocessor then detects
the battery type.
Resistor value
Battery type
1.8MΩ
560kΩ
220kΩ
Ni-MH
OPEN
Battery case
5-5. Key Input
Keys and channel selector circuit.
The signal from the keys and channel selector are directly
input to the microprocessor, as shown in Figure 11.
22
CIRCUIT DESCRIPTION
Battery status
The battery voltage is low but
the transceiver is still usable.
The battery voltage is low and
the transceiver is not usable
to make calls.
123
BATTLVL
IC7
CPU
Input voltage of S-terminal
Li-ion
0.3~1.3V
Ni-Cd
1.3~2.6V
2.6~5.0V
0~0.3V
6. Signaling Circuit
6-1. Encode
■ Low-speed data (QT, DQT)
Low-speed data is output from pin 30 of the CPU. The
signal passes through MOD amplifier (IC12 1/2), and goes to
the buffer amplifier (IC17 2/2). The signal is mixed with the
audio signal and goes to the VCO and TCXO (X501) modula-
tion input after passing through the D/A converter (IC16) for
BAL adjustment.
■ High-speed data (5-tone, DTMF)
High-speed data (HSD) is output from pin 4 of the CPU.
The signal passes through a low-pass CR filter and provides a
TX HSD tone and a RX HSD tone. TX HSD deviation making
an adjustment by microprocessor is passed through the
switch (IC14) and then applied to the audio processor (IC13).
The signal is mixed with the audio signal and goes to the
VCO and TCXO. The RX HSD tone is passed a summing am-
plifier (IC18). The D/A converter (IC16) for audio control, au-
dio power amplifier and then to the speaker.
■ MSK
MSK signal is output from pin 6 of IC13. The signal passes
through the D/A converter (IC16) and is routed to the VCO.
When encoding MSK, the microphone input signal is muted.
IC7
CPU
1
2
3
S
4
5
6
A
7
8
9
B
*
0
#
C
Fig. 11 Key input
Selector
SW2
AUX
SW
PTT
SW1
SW
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