Electrical Connections 7
Audio Connector
A 4-way RJ9 connector, as shown below,
allows a telephone handset to be plugged into
the modem, giving access to the microphone
andearpiecesignals.The connectormayalsobe
usedto drive other analogue audio sub-systems
or devices.
TheGM29isconfiguredtoworkwitharange
of handsets.
CAUTION! Not all handsets use the pin-outs
shown below for microphone and
earpiece.
If necessary, changes can be made to the
characteristicsof theaudio interface bysending
the modem appropriate AT commands.
RJ9 Handset Connector
Antenna Connector
Connect a GSM antenna to this port. Single
(900 or 1800MHz) or dual band
(900/1800MHz) antennas may be used. The
modem is fitted with a 50Ω, FME male coaxial
jack.
FME Connector
Signal Description
MICN Microphone negative input
BEARN Earpiece negative output
BEARP Earpiece positive output
MICP Microphone positive input
4321
1 MICN
2 BEARN
3 BEARP
4 MICP
Signal Description
RF RF input/output
GND Ground connection
GND
RF Signal
