Kenwood FleetSync TK-790 Скачать руководство пользователя страница 29

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TK-790/

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6. Control Circuit

The control unit consists of microprocessor IC and its

peripheral circuits. It controls the TX-RX unit and transfers
data to and from the control unit. The CPU (IC516) mainly
performs the following :
1) Switching between transmission and reception accord-

ing to the PTT signal input.

2) Reading channel, frequency, and program data from the

memory circuit.

3) Sending frequency data to the PLL.
4) Turning the squelch on and off according to the voltage

from the squelch circuit.

5) Controlling the audio mute circuit according to input de-

code data.

6) Sending encode data (QT, DQT).
7) Sending data to the D/A converter.

6-1. Memory circuit

A flash memory (IC519) with a capacity of 2Mbits con-

tains the transceiver control program for the CPU (IC516)
and data such as transceiver channels and operating fea-
tures.

This program can be easily written from an external de-

vices. Data, such as DTMF memories and operating status,
tuning data are programmed into the EEPROM (IC514).

6-2. Shift register

IC517 and IC523 are an interface IC for I/O port expan-

sion. It is used to expand the CPU (IC516) output ports.

6-3. D/A converter

IC512 is used as a conventional semi-fixed-resistor con-

verter. It sets the following :
1) RX sensitivity
2) Transmission power
3) Modulation level
4) Audio power
5) Frequency

6-4. Power supply circuit

D507 is a protection diode for the excess voltage

1) Turning the transceiver on/off with a power switch. Each

time you press the power switch, the IC501 output is al-
ternated. The output is feed through Q501, Q503 to turn
Q519 on. The power source is always supplied to the
IGN terminal. If 24V DC is supplied to the transceiver by
mistake, Q502 is turned on then Q503 and Q519 are
turned off to protect the transceiver (turned off).

2) Turning the transceiver on with a power switch, then

turning the transceiver off with the Timed Power Off
(TPO) function. POF is controlled by CPU’s TPO function.
POF is to turn the transceiver off. The POF logic signal is
feed through Q507 and Q506 then 8 pin of IC501 to turn
the transceiver off.

3) Turning the transceiver on with IGN SENS, then turning

the transceiver off with TPO function. If IGN is turned on,
Q543 and Q542 are turned on then the IC501 detects the
change. IC501 outputs the signal to turn Q541 off, then
Q503 and Q519 are turned on. When POF is detected by
6 pin of IC501, Q541 is turned on then Q503 and Q519
are turned off.

7. Signalling Circuit

7-1. Encode
• QT, DQT

The CPU (IC516) transmits the encode data selected by

the program. The data items are output from CPU pin 34.

The signal from this pin passes though the CR low-pass

filter and goes to the summing amplifier (IC510) in the mi-
crophone amplifier.

• DTMF

The DTMF-encoder (IC511) transmits the encode data.

The encode data is passed to the D/A convertor (IC512) for
DTMF deviation adjustment, and goes to IC505 in the IDC
circuit of the microphone amplifier.

7-2. Decode
• QT, DQT

The demodulated signal from CN502 pin 5 is amplified by

IC521 and passes through a low-pass filter (IC502) to re-
move audio components. The signal is input to pin 25 of the
CPU. The CPU digitizes this signal, and decodes the signal.

• 2 TONE

The demodulated signal from CN502 pin 5 is amplified by

IC504 and passes through a high-pass filter (IC518) and a
band-elimination filter (IC524) to remove QT and DQT.

This signal is amplified by IC521 and inputs pin 91 of the

CPU.

• DTMF

The demodulated signal from CN502 pin 5 is amplified by

IC504 and passes through a high-pass filter (IC518) and
band-elimination filter (IC524) to remove QT and DQT.

This signal inputs pin 1 of the DTMF decoder (IC525).

CIRCUIT DESCRIPTION

D507

AVR