Roadstar CLT-700, Руководство по обслуживанию

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5. Sending and Receiving of data signal
The sending MSK data comes out from TX_DATA of CPU (pin 49), and enters into pin
4 of U2(compandor).
It is modulated at RF block through the same path as audio signal.
The received MSK data which is demodulated at RF block with the same manner as
audio signal is going to the low path filter composed of U3B, C32, C33, C34, R30, R31
and R32. Filtered signal is comparated at U3A. The square wave (RX_DATA) from Q3
is fed to pin 48 of CPU.
6. Reset
When power switch (SW1) is pushed, pin 9 of U4 (RESET) is set from high to low.
This signal is used for CPU reset.
7. Power ON/OFF circuit
In case of setting power ON, if SW1 (power switch) is pushed, Q6 is ON then BS2
(pin12 of U4) becomes low level and VREG2 gives 3.2V power. The CPU is supplied
with this power of 3.2V(VREG2) and set BS2_CONT (pin 37 of CPU) to high level.
Then Q7 is switched ON, so BS2 remains low level even after SW1 is released.
In case of setting power OFF, if SW1 is pushed, pin 10 of CPU (PWR_OFF) becomes
high level and CPU makes BS0, BS1 and BS2_CON open state then all power is off.
In case that handset is put on charger cradle of base unit, automatically power
becomes ON because Q5 is ON.
8. Buzzer circuit
When the ring signal command comes from the base unit or the key pad is pushed, the
buzzer control signal comes from RING_ON of CPU (pin 17) and it makes Q12 ON and
OFF, then the buzzer (BZ1) makes ring or beep sound.
If the RING_LEVEL (pin 25 of U5) is set on high, then R42 is connected to R41 in
parallel and the sound will be loud.
And if the buzzer H/L is set on low, then the sound will be low.
9. Charge and detect circuit
If handset is cradled at base unit, the charge current is supplied from base unit through
the JP2 (charge contact). Charging current flows to the battery through D1.
At that time the Q4 will be on and the CHARGE of CPU (pin 22) become low, then the
CPU acknowledges the condition of charging.