An error signal detection method and apparatus for an optical recordingreproducing system. Traffic on a commercial website is constantly monitored by a web analytics tool, which collects traffic measurements of hits, button presses, enquiries, purchases etc, as well as the referrer URL of a site such as a social networking site through which the commercial website is accessed. Chargingdischarging limiting circuit includes charge element, discharge, control unit, charging current detection unit, voltage detection unit, valuable reference voltage source, and voltage comparison unit. If it is determined that an acknowledgement signal from the access point has not been received by the transmitting station, then the alarm signal is wirelessly re-transmitting from the transmitting station during at least one of the time intervals in which the relaying station is awake.