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RH-128
Baseband Description and Troubleshooting
Audio Faults
No Sound in Earpiece & Microphone (refer to Audio PA Circuit design)
Enter the test mode ’LoopBack’ by pressing test order #0000# then press ‘calling key’ when the
No Sound in Earpiece & Microphone message appears.
1. If the test result is normal, it indicates that the ‘Loopback’ circuit (receiver & microphone) is OK
in hardware connection. The bottom socket should be checked whether it has been short
circuited to the ground. If it is grounded, the mobile phone software will detect that the earpiece is
in the Insert Mode, which sets the mobile phone in earpiece mode, and it means that both of the
earpiece and the microphone do not work.
2. If the test result shows that the ‘Loopback’ is abnormal, the fault reason should be picked up
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