Matsushita Electric KX-TCD952NLB, Service Manual

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ground is provided on J103. The bi-directional serial data line is split into two at IC101 pin 27
(input) and pin 26 (output). Data rate is 9600 baud J103. D105provides ESD protection, and R117
and C146 provide RF de-coupling.
8.2.8. BUZZER CIRCUIT (SEE Fig. 19)
A square-wave signal from IC101 pin 41 (TP103) is used to sound the buzzer via switching
transistor T101 (TP101). Various tones and cadences are used dependent on function. Buzzer
volume is varied by changing the duty cycle of the drive waveform. D101 provides quenching of
back-emf generated when T101 turns off.
8.2.9. OFF HOOK AND CALLER LED´S (SEE Fig. 19)
When the Handset is in “Talk” mode, the Off-Hook LED D102 is switched on by transistor T102
(on), using a control line from pin 28 of IC101 (TP106). “On the TCD952 the caller” LED is
switched via T103.
8.2.10. AUDIO PATH-RX AUDIO-LINE INPUT (SEE Fig. 20)
Audio from the Line Interface TXAF (TP123) enters the BBIC on pin 58. R111 and C113 are to
balance the line input 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 22 as TRADAT, (TP132).
8.2.11. AUDIO PATH - TX AUDIO - LINE OUTPUT (SEE Fig. 20)
Audio from the receiver RECDAT enters the BBIC on pin 20 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 line
output amplifier, and balanced audio is output on pin 63, and fed as RXAF (TP120) to the Line
Interface.
Circuit Diagram
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