User's Manual

UE910 V2 Hardware User Guide
1VV0301065 Rev.1 – 2013-12-12
Reproduction forbidden without written authorization from Telit Communications S.p.A. - All Rights Reserved. Page 42 of 67
9. Audio Section Overview
The UE910 V2 provides an analog audio interface and digital audio interface.
9.1. Analog Audio Interface
The UE910 V2 provides an analog audio interface; one differential input for audio to be
transmitted(Uplink) and a balanced output for audio to be received(Downlink).
The bias for the microphone has to be as clean as possible; the first connection (single ended) is
preferable since the Vmic noise and ground noise are fed into the input as common mode and then
rejected. This sounds strange; usually the connection to use in order to reject the common mode is the
balanced one. In this situation we have to recall that the microphone is a sound to current transducer,
so the resistor is the current to tension transducer, so finally the resistor feeds the input in balanced
way even if the configuration, from a microphone point of view, seems to be un-balanced.