net/templates/freeswitch/conf/autoload_configs/fax.conf.xml

<configuration name="fax.conf" description="FAX application configuration">
    <settings>
	<param name="use-ecm"		value="true"/>
	<param name="verbose"		value="false"/>
	<param name="disable-v17"	value="false"/>
	<param name="ident"		value="SpanDSP Fax Ident"/>
	<param name="header"		value="SpanDSP Fax Header"/>

	<param name="spool-dir"		value="/tmp"/>
	<param name="file-prefix"	value="faxrx"/>
    </settings>
</configuration>