Abstract: Provided is a security technique using a mobile phone terminal and a compact base station that reduce the disadvantages when the mobile phone terminal is left in the house or office or is left without being carried. A base station of a mobile communication system includes a radio unit that wirelessly communicates with a mobile station through wireless communication, a communication unit that communicates with the mobile communication system through a communication line, and a control unit that determines whether there is a location-registered mobile station when a predetermined condition is satisfied and controls the communication unit to transmit a predetermined message to a predetermined counterpart through the communication line when there is no location-registered mobile station.

Abstract: A PC card terminal device operates while supplied with power from a computer in which the PC card terminal device is mounted. A transmission power controller determines a first marginal transmission power, and increases the transmission power of the PC card terminal device up to the first marginal transmission power, and further increases the transmission power increased to the first marginal transmission power at an increasing rate smaller than the increasing rate of the above-mentioned increase.