The Echo Fox radio system was used for Presidential communications between aircraft and a series of AT&T facilities throughout the United States.  The system operated on 407.850/415.700 mhz and was turned down several years ago.  The base stations were General Electric with the latest ones in the MASTR series.  I recently found some of the aircraft "mobiles" for sale on the internet below.  Note that they are a modified Motorola Mitrek mobile.