Electronic device including separable and independently operable personal digital assistant and mobile communications device

An electronic device comprising:

• a personal digital assistant including a casing body having an outer mounting surface that is provided with a first electrical connector;
• a mobile communications device including
• a housing having a first mounting surface disposed removably on said outer mounting surface of said casing body, said first mounting surface being provided with a second electrical connector that is connected electrically and detachably to said first electrical connector to permit signal transmission between said personal digital assistant and said mobile communications device,
• a battery pack having a second mounting surface disposed removably on said first mounting surface of said housing and coupled electrically to said mobile communications device for supplying electric power thereto, and
• a fastening unit provided on said housing and said battery pack for fastening releasably said battery pack on said housing when said first mounting surface of said housing is removed from said outer mounting surface of said casing body and when said second mounting surface of said battery pack is disposed on said first mounting surface;
• and
• an engaging unit provided on said outer mounting surface of said casing body and said first mounting surface of said housing to permit engagement between said personal digital assistant and said mobile communications device when said second mounting surface of said battery pack is removed from said first mounting surface of said housing and when said first mounting surface of said housing is disposed on said outer mounting surface of said casing body.