Portable telephone set having a power controller causing a current charging of a battery to be held constant

A portable telephone set, comprising;

• a power supply in which a battery is employed;
• a charging detector for detecting whether a charger for charging current into said battery is connected to said power supply, wherein said charging detector generates a detection signal when it detects that said charger is connected to said power supply;
• a power controller which turns on power of said portable telephone set when said power controller receives said detection signal from said charging detector, said power controller thereby causing said current charging said battery to be held constant at a predetermined value;
• means for indicating a charging condition, wherein said indicating means operates when said detection signal is generated;
• and
• means for measuring a time period during which said detection signal is generated, wherein said indicating means displays said time period;
• wherein said charging detector comprises means for detecting whether said charger is connected to said power supply, wherein said detecting means detects a voltage generated on a terminal of said power supply when said charger is connected to said power supply;
• wherein said detecting means detects a voltage difference between said voltage generated on said terminal and a reference voltage, said detecting means generating said detecting signal when detecting said voltage difference;
• and
• wherein said detecting means generates aid detection signal when said voltage difference exceeds a predetermined value.