三.TRANSMISSION/RECEPTION SELECTOR CIRCUIT
The transmission output is passed through the transmission/reception
selector circuit and low-pass filter to the antenna. The transmission/reception
selector circuit, which consists of diodes D161, D160, D261 and D262, is turned
on during transmission and off during reception to switch the signal.
四.DIGITAL CONTROL CIRCUIT
SIDE KEY AND ENCODER CIRCUIT
The signal from side key and encoder is directly input to the processor.
Reset and backup circuit
When turn on the power, a positive pulse is output from the reset circuit
consisting of D831,C831 and R831 to the third feed of reset terminal on U821
microprocessor. When turn off the power,U517 detects a 3.3 V drop, and output
a low signal, it outputs data to U811 and enter backup mode.
BATTERY VOLTAGE TEST CIRCUIT
Power supply voltage after partial pressure input to the microprocessor
analog interface
BATTERY SAVE CIRCUIT
The squelch is off during receive. The power circuit enters battery save
mode if no key has been pressed for five seconds.
The circuit is controlled by microprocessor directly.
To Next Page
Loading...
Need help?
General
