Panasonic KX-TCD705RUM Service Manual page 26

KX-TCD705RUM / KX-TCD705RUS
6.1.6. AUDIO PATH - TX AUDIO (SEE Fig. 25)
The audio signal from the microphone (TP23) enters the BBIC at pin 44. RF decoupling and 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.
6.1.7. 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.
6.1.8. 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.
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