A control circuit for use in an electrical apparatus , comprising: a switch element disposed between a secondary battery built in the electrical apparatus and a load which consumes power supplied from the secondary battery to implement a function required for the electrical apparatus ; a control element configured to keep the switch element in an off state until use of the electrical apparatus is started by a user and switch on the switch element when use of the electrical apparatus is started by the user; a power supply switch for starting operation of the load , the power supply switch being configured to be switched on or off by the user; a monitoring circuit configured to monitor a state of the power supply switch and to detect a battery remaining amount of the secondary battery ; a system control circuit ; and a connection terminal configured to accept power supply from an external power supply source; the monitoring circuit being connected to the secondary battery directly without the intervention of the switch element , wherein the switch element is configured to electrically connect the secondary battery with the connection terminal , the system control circuit and the load , when being switched on, and to electrically disconnect the secondary battery from the connection terminal , the system control circuit and the load , when being switched off, the switch element remaining in an off state until use of the electrical apparatus is started by the user, the switch element being switched on when the monitoring circuit detects an operation for switching on the power supply switch by the user, and the switch element being switched on when power supply from the external power supply source to the connection terminal is started. a switch element disposed between a secondary battery built in the electrical apparatus and a load which consumes power supplied from the secondary battery to implement a function required for the electrical apparatus ; a control element configured to keep the switch element in an off state until use of the electrical apparatus is started by a user and switch on the switch element when use of the electrical apparatus is started by the user; a power supply switch for starting operation of the load , the power supply switch being configured to be switched on or off by the user; a monitoring circuit configured to monitor a state of the power supply switch and to detect a battery remaining amount of the secondary battery ; a system control circuit ; and a connection terminal configured to accept power supply from an external power supply source; the monitoring circuit being connected to the secondary battery directly without the intervention of the switch element , wherein the switch element is configured to electrically connect the secondary battery with the connection terminal , the system control circuit and the load , when being switched on, and to electrically disconnect the secondary battery from the connection terminal , the system control circuit and the load , when being switched off, the switch element remaining in an off state until use of the electrical apparatus is started by the user, the switch element being switched on when the monitoring circuit detects an operation for switching on the power supply switch by the user, and the switch element being switched on when power supply from the external power supply source to the connection terminal is started. <EOS>