Filter
Top Products
HUAWEI MG323 GSM M2M Module
Hardware Guide
Description of the Application Interfaces
Issue 04 (2011-08-22)
Huawei Proprietary and Confidential
Copyright © Huawei Technologies Co., Ltd.
24
Figure 3-11 ESD protection circuit on the SIM card
3.8 Audio Interface
3.8.1 Overview
The MG323 module provides two types of audio interfaces: one is for handsets, the
other is for headsets. The audio interfaces of the MG323 module support input from
handset microphones and headset microphones, and provide output that supports 32
Ω handsets and 16 Ω headsets. Differential signal lines are recommended for the
microphone interface and the speaker interface. Single-ended signal lines are not
recommended. The reception gain can be adjusted by using software. A microphone
with an equivalent load of 2.2 kΩ is recommended, because both the pull-up resistor
and the pull-down resistor of the two types of differential signal lines for the
microphone are 1 kΩ.
3.8.2 Speaker Interface
The MG323 module provides two types of audio interfaces that respectively support
32 Ω handsets and 16 Ω headsets. 33 pF capacitors are added for filtering radio
frequency interference. Differential signal lines are recommended for the speaker
interface. Consider the drive capability of the module when using a speaker with
greater power.