MTX-H15 UMTS-HSDPA terminal modem | http://www.matrix.es |
3.2 Audio Connector
A 6-way 4-poles RJ connector, as shown below, allows a telephone handset to be plugged into the modem, giving access to the microphone and earpiece signals. The connector may also be used to drive other analogue 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-H15 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.
Audio handset connection.
Audio signal descriptions are listed below:
Pin | Signal |
0 | Not connected |
1 | MICN |
2 | EPN |
3 | EPP |
4 | MICP |
5 | Not connected |
Dir Description
IMicrophone negative input
OEarpiece negative output
O | | Earpiece | positive |
| | output | |
IMicrophone positive input
A power supply for electret microphones is already feeded to MICP connection.
Microphone signals are fed via the MICP and MICN pins to an analog-to-digital converter (ADC) and the DSP. The DSP application core calculates e.g. digital gains, sidetone, echo cancellation or noise suppression depending on the current configuration of the audio path. The processed speech samples are passed to the speech encoder.
Received samples from the speech decoder are passed to the digital-to-analog converter (DAC) after post processing (frequency response correction, adding sidetone etc.). The loudspeaker signal is routed via EPP and EPN pins. No gain setting is available in the earphone amplifier. The volume is controlled in the digital data stream by the DSP only. The default audio mode (AT^SNFS=1) is optimized for the Votronic HH-SI- 30.3/V1.1/0 handset and used for type approving the Siemens reference configuration. The second audio mode (AT^SNFS=2) is intended to be used together with a subscriber line interface circuit (SLIC) providing an analogue telephone interface in a router device.
Both audio modes have fixed parameters that cannot be modified.
MTX-H15 User Manual V.2.0Pag. 14
Preliminary. Subject to change without prior notice
