enhanced call routing In the advanced intelligent network (AIN) specifications, a network-based enhancement to toll-free calling in the public switched telephone network (PSTN). The callers are presented with options that enable them to specify their needs and then be connected with the offices or individuals best able to satisfy them. See also  AIN  and  PSTN.  74570c05.qxd  9/11/07  12:20 PM  Page 170  |