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signal conditioning are provided by C17, R21, C14 and C25.
In the BBIC the signal passes through the analogue section where it is amplified and converted
to a digital audio stream signal. The burst mode controller processes this stream performing
encryption and scrambling, adding the various other fields to produce the GAP standard DECT
frame, assigning to a time slot and channel etc. to emerge on pin 14 as TXDA.
7.1.7. AUDIO PATH - RX AUDIO (SEE Fig. 25)
Audio from the receiver RXDA enters the BBIC on pin 10 as GAP standard DECT frames. It
passes through the decoding section burst mode controller where it separates out the frame
information and performs de-encryption and de-scrambling as required. It then goes to the DSP
where it is turned back into analogue audio. This is amplified by the analogue front end and
emerges at pin 40 and 41. The telephone speaker is driven directly from the BBIC output ports.
The hands-free loudspeaker at SP+ and SP- is used to generate the ring alarm. When the
handset is not in hands-free mode the HF_AM1 amplifier is deactivated by the SP_CTR control
signal at pin 93 from the BBIC.
The earpiece speaker LS1 is driven directly from the HON and HOP output lines, pins 40 and 41,
without any amplification.
A 2.5mm jack J6 is provided for connecting a headset.
7.1.8. CLOCK GENERATION (SEE Fig. 25)
A single clock generator in the BBIC uses an external crystal X1 to derive all clock frequencies
used in the handset. The crystal is tuned to the exact frequency of 10.368 MHz during
manufacture.
The BBIC provides a reference clock signal SYRI (pin 21, TP101) which is used to drive the PLL
circuitry in the RF module. The basic data rate for TXDA (pin 14) and RXDA (pin 10) is 1.152
Mbits/s, which is 10.368MHz divided by 9.
Circuit Diagram
29
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