A battery charging system includes a battery pack (106) and charger (102). Battery pack (106) includes a selectable magnetic field generator (202) which is activated by radio controller (206) when radio (104) changes states. A Hall-effect switch (204) located in either charger (102) or battery (106)...http://www.google.co.uk/patents/US5606241?utm_source=gb-gplus-sharePatent US5606241 - Apparatus for determining radio state during charging in order to provide charge compensation
