Analog Audio Interface - MTX -3G-JAVA-IoT User Manual

4.9 Analog audio interface

Those MTX-IoT models ordered with Audio option (A) have a 6-way 4-pole RJ connector, as shown
below, allowing a telephone handset to be plugged into the modem and giving access to the
microphone and earpiece signals. The connector may also be used to drive other analog audio sub-
systems or devices.
The audio interface provides one analog input for a microphone and one analog output for an earpiece.
•
The microphone input and the earpiece output are balanced
•
For electret microphones a supply source is implemented
•
The MTX-IoT is pre-configured to work with a range of handsets, the audio interface is flexible
and its performance can be configured, using AT commands, to match a particular handset or
audio subsystem
•
Earpiece outputs are short-circuit protected
Pin Signal
1 Not connected
2 MICN
3 EPN
4 EPP
5 MICP
6 Not connected
To suit the different types of accessories, the audio interfaces can be configured for different audio
modes. The electrical characteristics of the voiceband part vary with the audio mode. For example,
sending and receiving amplification, sidetone paths, noise suppression etc. depend on the selected
mode and can be altered with AT commands (except for mode 1).
Both analog audio interfaces can be used to connect headsets with microphones or speakerphones.
www.mtxm2m.com
Direction Description
Input Microphone negative input
Output Earpiece negative output
Output Earpiece positive output
Input Microphone positive input
2017/07 v1.2
MTX M2M® by MATRIX ELECTRONICA S.L.U
MTX-xG-JAVA-IoT Family
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