Global Positioning Systems (GPS) utilise 24 satelites that circle the earth in a very precise orbit and transmit information to the earth. These signals are received by GPS systems to provide the user with location and navigation guidance. The Garmin Forerunner 101 is a compact, wrist mounted, GPS that was originally developed for runners and cyclists, but can be equally used on horseback. Operating form 2 x AAA batteries supplied (typical life 10-15 hours constant use) The 101 provides the user with a multitude of information from its large l.c.d screen including Timer (Stopwatch), Speed (in mph or kmph) distance (in miles or kilometers) By scrolling through the on screen menu the user can access information and features on the following * Ride History - By Day, Week or in Total * Training Assistant allows the user to set, auto pauses auto lap, interval training, speed and time alerts or activate the Virtual Partner (helps you active training goals) *  Navigation allows the user to mark a given location, find a given location, return back to the starting point by utilising the on screen electronic breadcrumb trail of where you have travelled, and to orient the on screen map (if selected) by a North reference or ahead (the direction you are moving) Another feature of the 101 is that the front main screen can be customised to display alternative data including Lap Time, Total Distance, Elevation, Time of Day etc. The Foreunner 201 differs from the 101 unit in that it comes complete with battery charger and rechargeable batteries (typical life 10-12 hours constant use). It is also provided with an inteface cable that allows the data in GPS to be downloaded to a personal computer via Free downloadable software from the Garmin website Both units are supplied with comprehensive instruction Manuals