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9.1.4. AUDIO PATH - TX AUDIO (SEE Fig. 27)
Balanced audio from the microphone (TP40 and TP41) enters the BBIC at pins 61 and 63. A balanced bias voltage for the
(“electret” type) microphone is supplied by the BBIC from pins 60 and 64 via R31 and R32. This supply is de-coupled by R22, R27,
C21, C28, and C22. RF de-coupling of the microphone signal is provided by R27, C25, R28, C26, R24, R25, and C20. The
microphone audio signals are coupled to the BBIC via C22 and C23, which provide some high pass filtering.
In the BBIC audio passes through the gain-controlled microphone amplifier, into the ADC part of the codec, where it is sampled and
turned into digital data. The burst mode controller then processes this raw data (called the B-field) performing encryption and
scrambling, adding the various other fields that go together to produce the GAP standard DECT frame, assigning to a time slot and
channel etc. The data then passes through the gaussian filter to emerge on pin 20 as TRADAT.
(“electret” type) microphone is supplied by the BBIC from pins 60 and 64 via R31 and R32. This supply is de-coupled by R22, R27,
C21, C28, and C22. RF de-coupling of the microphone signal is provided by R27, C25, R28, C26, R24, R25, and C20. The
microphone audio signals are coupled to the BBIC via C22 and C23, which provide some high pass filtering.
In the BBIC audio passes through the gain-controlled microphone amplifier, into the ADC part of the codec, where it is sampled and
turned into digital data. The burst mode controller then processes this raw data (called the B-field) performing encryption and
scrambling, adding the various other fields that go together to produce the GAP standard DECT frame, assigning to a time slot and
channel etc. The data then passes through the gaussian filter to emerge on pin 20 as TRADAT.
9.1.5. AUDIO PATH - RX AUDIO (SEE Fig. 27)
Audio from the receiver RECDAT (TP54) enters the BBIC on pin 18 and passes through the clock recovery circuit. The burst mode
controller separates out the B-field data, and performs de-encryption and de-scrambling as required. It then goes to the DAC part
of the codec where data is turned back into analogue audio. The audio signal is amplified by the gain-controlled earpiece amplifier,
and balanced audio is output on pins 65 and 66, and fed to the earpiece (TP31 and TP32). The leads feeding the earpiece are RF
de-coupled by C15 to R22, C17, C16, R23, and C18. C19 provides low pass filtering.
controller separates out the B-field data, and performs de-encryption and de-scrambling as required. It then goes to the DAC part
of the codec where data is turned back into analogue audio. The audio signal is amplified by the gain-controlled earpiece amplifier,
and balanced audio is output on pins 65 and 66, and fed to the earpiece (TP31 and TP32). The leads feeding the earpiece are RF
de-coupled by C15 to R22, C17, C16, R23, and C18. C19 provides low pass filtering.
Circuit Diagram
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KX-TCD953RUB
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