If you already have the page number, say 5, pass it in after your url param:
url: "/fax/fax_out_ajax/",
data: {'page': 5},
If you have the page number in the variable pageNumber
, do:
url: "/fax/fax_out_ajax/",
data: {'page': pageNumber},
If you don't already have the page number, get it from somewhere else on the page:
url: "/fax/fax_out_ajax/",
data: {'page': $('#page_number').val()},