Kenwood NXR-5700, Service Manual

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1-20 (No.RA033<Rev.001>)
2.6.5.4 DSP
The DSP circuit consists of a DSP (IC150) and processes the base band signal. The DSP operates on an external clock of 18.432MHz
(the same as the IC50), the I/O section operates at 3.3V and the core section operates at 1.6V. The DSP carries out the following
processes:
 Digital Processing
• 4Level FSK and Baseband filter processing
• Vocoder processing between audio codec and modulation/demodulation
• CAI processing, such as error correction encoding/decoding and interleaving
• AFC loop control
• Frame synchronization and Time tracking
• Data scrambling
 Analog FM Processing
• Pre-emphasis/De-emphasis
• QT/DQT encoding/decoding
• DTMF encoding/decoding
• Compressor/Expander processing
• Voice scrambler processing
 Audio or Modulation function
• Transmit/Receive audio filtering processing
• Microphone amplifier AGC processing
• Audio soft mute processing
• Modulation level processing
• Squelch Filtering
 Other function
• Voting tone
• CWID
• Courtesy tone
• Repeater operating
• Analog/Digital Mixed mode
2.6.5.5 Frame transmitter and receiver circuit
J410 and J411 are connectors to synchronize with other repeaters. Differential rectangular wave 12.5Hz or 25Hz is input to and output
from this connector for synchronizes multiple repeaters.
In the repeater system, any given repeater outputs synchronizing signal and synchronous signal is input to other remaining repeaters.
With regard to output of synchronous signal, frame signal generated by DSP (IC150) is differentially output by IC410.
With regard to input of synchronous signal, IC410 receives differential signal, and it is input to the interruption of DSP (IC150).