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owa4x provides a ground connection for all interfaces, digital I/Os, RS485, CAN
and analog inputs.
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Audio output is of BTL type (Bridge Tied Load). That means none of the
speaker signals are internally connected to ground.
Never connect any terminal of the loudspeaker output to ground or power
supply as it may damage either the speaker or the owa4x.
The recommended external loudspeaker has the following features:
• Impedance higher than 3 >
• Required power handling: 1.5 W over 8 > and 2.5 W over 4 >
• Frequency responser between 300 Hz – 3.4 Khz (recommended)
Microphone input in of unbalanced type (signal is referred to ground) and
accepts electret type microphones. Those are the type of microphones most
widely used for consumer purposes. Yet they provide very good performance at
a very low price. They need a clean, very stable power supply (usually called
VBIAS) that is provided by owa4x. Signal Input and VBIAS share the same pin in
the connector, as this is the connection usually found in commercially available
microphones.
Microphone sensitivity is usually expressed in terms of voltage/acoustic
pressure (dB/µPa.). Higher value means best sensitivity, so a microphone rated
at -46 dB/µPa is worst than other at -36 dB/µPa
The recommended features of the microphone are:
• Use only electret type microphones
• High sensitivity is recommended for hands-free applications (in the
range of -46 dB/?Pa
• Impedance equal or higher than 1 K>
• Connector with signal and BIAS tied together
4.1.4.6 microSIM Card Holder
The SIM Card Holder is a push-push connector and it is for the GSM/GPRS
service.
Connector type Push push microSIM holder
Card type supported 3V and 1.8V
Location Rear panel
6 SIM card holder characteristics
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General