TK-260G/270G
CIRCUIT DESCRIPTION
6. Control Circuit
The control circuit consists of a microprocessor (IC13) and its peripheral circuits. It controls the
(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.
3) Low battery warning
The battery voltage is monitored by the microprocessor (IC13). When the battery voltage falls below the voltage set by the Low Battery Warning adjustment, the LED flashes red to notify the operator that it is time to replace the battery. If the battery voltage falls even more (approx. 5.8V), a beep sounds and transmission is stopped.
Low battery warning | Battery condition |
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The red LED flashes during | The battery voltage is low but |
transmission. | the transceiver is still usable. |
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The red LED flashes and a | The battery voltage is low and |
continuous beep sounds | the transceiver is not able to |
while PTT is pressed. | make calls. |
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1)Frequency shift circuit
The microprocessor (IC13) operates at a clock of 9.8304MHz. This oscillator has a circuit that shifts the frequency by BEAT SHIFT SW (Q31).
2)Memory circuit
Memory circuit consists of the CPU (IC13) and a flash memory (IC12). A flash memory has a capacity of 2M bits that contains the transceiver control program for the CPU and data such as transceiver channels and operating features.
This program can be easily written from an external device. Data, such as DTMF memorise and the operating status, are programmed into the EEPROM (IC10).
●Flash Memory
Note : The flash memory holds data such as written with the FPU
●EEPROM
Note : The EEPROM stores tuning data (Deviation, Squelch, etc.).
Realign the transceiver after replacing the EEPROM.
IC13IC10
CPU 
EEPROM
FLASH
IC12
7. Optional Board Terminal
Terminals for mounting the option board are provided at the bottom edge of the
Optional Board Terminal Function (CN5)
Pin | Name | I/O | Function |
1 | GND | - | GND |
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2 | SB | O | Power output after power switch |
3 | AUX3 | I/O | Board control |
4 | TXAFI | I | Modulation output from board |
5 | AUX2 | I/O | Board control |
6 | AUX6 | O | Board control |
7 | AUX1 | I | Board control |
8 | AUX5 | O | Board control |
9 | AUX4 | O | Board control |
10 | TXAFO | O | Modulation input to board |
11 | 5C | O | 5V |
12 | RXAFO | O | Received signal input to board |
13 | NC | - | NC |
14 | RXAFI | I | Received signal output from board |
15 | NC | - | NC |
16 | ALTTONE | I | ALART TONE output form board |
17 | NC | - | NC |
18 | NC | - | NC |
19 | NC | - | NC |
20 | GND | - | GND |
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Fig. 9 Memory circuit
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