Read Panasonic KX-TCD961EB Service Manual online
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KX-TCD961EB
1.10 FACTORY SERIAL PORT (SEE Fig. 31)
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 J6 (TP65), and a ground is provided on J7. The bi-directional serial
data line is split into two at IC1 pin 27 (input) and pin 26 (output). Data rate is 9600 baud or 115.2 kBaud.
D13 provides ESD protection, and R37 and C56 provide RF de-coupling.
1.11 BUZZER CIRCUIT (SEE Fig. 35)
A square-wave signal from IC1 pin 45 is used to sound the buzzer via switching transistor T5 (TP22). Various tones
and cadences are used dependent on function. Buzzer volume is varied by changing the duty cycle of the drive
waveform. D11 provides quenching of back-emf generated when T5 turns off.
1.12 BATTERY SUPPLY (SEE Fig. 35)
The three cell NiCd/NiMH rechargeable battery supplies the handset via 2A fuse (actually a coil), and is de-coupled by
C3 and C4. It directly supplies T3 in the baseband section, and also the Tx PA in the RF Section. It also supplies IC1
(de-coupled by C9), and most of the RF Section (VCC-OC) (decupled by R35 and C47, C48 and VCC-PA).
1.13 MAIN 3V REGULATOR (SEE Fig. 35)
The BBIC measures the battery voltage on pins 58 using an internal ADC. If the battery voltage is below 3.36 V, TC3 is
switched to power off mode. R7 and C5 provide a reset pulse (TP84) used for resetting the BBIC when power on.
The +3 V supply (TP10) is fed to the BBIC, Flash PROM, EEPROM, and Display Driver.
1.14 BATTERY CHARGING CIRCUIT (SEE Fig. 35)
The charge circuit is designed to operate with a constant current charger in the base. L1, L2, D2 and D4 protect
against electro-static discharge (ESD). The charging current from the base is turned on and off by T1 using a control
signal from the BBIC (pin 39, TP6) via T2. R3 provides initial current in the event of a totally flat battery, and D6 pro-
tects against the high voltage present on the charge contacts if there is no battery in the handset. R4 and R5 provide a
signal for the BBIC to detect (pin 40) that the handset had been placed on the base charger. If the handset is off, it will
be switched on, and charging will start.
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