TK-2202L
5
X2
XIN
XOUT
IC405
Q407
H : OFF
L : ON
Q408
H : OFF
L : ON
BSHIFT
IC405
CPU
IC406
EEPROM
SB
R404
R406
BATT
88
IC405
CPU
Fig. 3 Low battery warning
Ni-Cd Battery
Ni-MH Battery
Li-ion Battery
(1)
6.2V
6.2V
6.2V
(2)
5.9V
5.9V
5.9V
CIRCUIT DESCRIPTION
1. Control Circuit
The control circuit consists of a microprocessor (IC405) and
its peripheral circuits. It controls the TX-RX unit. IC405 mainly
performs the following:
(1) Switching between transmission and reception by the
PTT signal input.
(2) Reading system, group, frequency, and program data
from the memory circuit.
(3) Sending frequency program data to the PLL.
(4) Controlling squelch on/off by the DC voltage from the
squelch circuit.
(5) Controlling the audio mute circuit by the decode data input.
(6) Transmitting tone and encode data.
1) Frequency Shift Circuit
The microprocessor (IC405) operates at a clock of
7.3728MHz. This oscillator has a circuit that shifts the
frequency by BEAT SHIFT SW (Q407,Q408).
A beat sound may be able to be evaded from generation if
“Beat Shift” is set to ON when it is generated in the internal
spurious transmission modulated sound of a transceiver.
2) Memory Circuit
Memory circuit consists of the CPU (IC405) and an EEPROM
(IC406). An EEPROM has a
capacity of 8k bits that contains
the transceiver control program for the CPU and data such
as transceiver channels and operating features.
3) Low Battery Warning
The battery voltage is checked using by the microprocessor.
The transceiver generates a warning tone when the battery
voltage falls below the warning voltage (2) shown in the table.
(1) The red LED blinks when the battery voltage falls below
the voltage (1) shown in the table during transmission.
Note:
During reception, transceiver constantly checks the battery
level. When the battery level drops near to 5.9V, the red
LED blinks and low battery warning tone is generated.
(2) The transceiver immediately stops transmission when
the battery voltage falls below the voltage (2) shown in
the table. The warning tone sounds while the PTT
switch is pressed.
Fig. 1 Frequency shift circuit
Fig. 2 Memory circuit
