Read Panasonic KX-TCD951GB / KX-TCD955GC Service Manual online
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KX-TCD951GB/KX-TCD955GC
1.6 LOCATOR KEY (SEE Fig. 19)
The keyboard “Locator (Page)” button is connected to pin 68 (TP154) of the IC101. When pressed the base transmits
a message to the handset, which then beeps.
1.7 FACTORY SERIAL PORT (SEE Fig. 19)
In order to communicate with the handset during manufacture and servicing (using a PC) a serial data link has been
provided. Serial data input/output is provided on J102 (TP151), and a 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. D105
provides ESD protection, and R117 and C146 provide RF de-coupling.
1.8 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.
1.9 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 KX-TCD955EC the CALLER LED is switched via T103.
1.10 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
(differential) audio input of IC101, and C110 and C112 are for RF de-coupling. In the BBIC audio passes through the
gain-controlled 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).
1.11 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.
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