Specifications

25
unmatched, the busy L.E.D. (Yellow) would be shown.
CTCSS/DCS ENCODE CIRCUITS
During TX encode, the tone squelch digital signal is produced as a 3-bit parallel word at Pins 33,
34, and 35 of the micro controller (IC401). The 3-bit digital signal is converted to an analog
signal by resistors R481, 482 and 483. The analog signal is fed into Pin 1of IC409 and out on
Pin 15 (IC409) and then fed into Pin 8 of IC410 (6th order Butterworth clock tuned low pass
filter). The filtered encode output from Pin 3 (IC410) is fed to IC411-A and RV402 (sub-audible
gain control), the output of IC411-A is then fed to the audio mixer circuit of the RF board.
TWO TONE DECODE CIRCUITS
Two tone uses frequency with audio. Discriminated audio from the RF board is inputted to the
comparator (two tone decoder : IC403-B) which forms the squaring circuit for the decode signal.
The signal is output from Pin 7 of IC403-B and fed into IC401 (MCU) where it is compared
whether it is matched with preprogrammed data or not. If matched valid data is decoded, which
is shown by a green L.E.D. on the top panel of the radio and audio is released through pin 9 of
the DB-15 Connector. If unmatched, the busy L.E.D. (Yellow) is shown.
RSSI DETECTOR
From the RF board, the RSSI (Received Signal Strength Indicator) signal flows to Pin 31 of
IC401(MCU) through R513. Micro controller unit (IC401) detects received signal level using the
inner 8-bit ADC(Analog to Digital Converter). The output of ADC is compared with the
programmed RSSI level. If the MCU detects existence of a received signal through these
comparison a yellow L.E.D. is shown on the top panel of the radio.
EEPROM
RX / TX channel and RSSI detection level as well as other data from the programmer are stored
in the EEPROM. The stored data is retained without power supply. This is a non-volatile
memory and re-programmable. IC402 is an EEPROM with 4096 (8 x 512) capacity and data is
written and read serially.