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GSM antenna option, then follow the above guideline for the external antenna. The backup battery option can be attached to the bottom of the T21 unit as shown in the picture above or located beside the unit. C shaped Velcro is provided for this purpose. The battery should be charged for 3.5 hours prior to use and will power the unit for 48 hours under normal...
2.4.3 External Antenna Option This option is needed when it is not possible to install the T21 in a location where the GPS or GSM antenna will work. This option allows the antennas to be located in a different location within the vehicle.
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