I don’t think that it has any particularly important additional function over the GM-862 Quad, although you should probably verify that with Telit’s documents:
GE-863 Quad http://www.telit.com/en/products.php?p_ … c=show&p=9
GM-862 Quad http://www.telit.com/en/products.php?p_ … c=show&p=4
It’s main advantage of which I am aware is that it’s cheaper.
Trevor