Abstract: The present invention provides a repeater which automatically closes a dynamically opened port in accordance with prior setting, the repeater including: a port mapping table where a global IP address and an external port number, or an external port number on the Internet is associated with a local IP address and an internal port number of a terminal connected to a LAN; a control unit which, receiving a communications packet to which an external port number is specified, converts the external port number to an internal port number based on the port mapping table and transfers the internal port number to the LAN; a timer unit which counts the unoccupied time of the port after transferring a communications packet to which an external port number is specified; and a port management unit which checks whether the registered machine is present on the LAN and in case it is absent, deletes registration concerning the external port number from the port mapping table.

Abstract: The present invention provides a repeater which automatically closes a dynamically opened port in accordance with prior setting, the repeater including: a port mapping table where a global IP address and an external port number, or an external port number on the Internet is associated with a local IP address and an internal port number of a terminal connected to a LAN; a control unit which, receiving a communications packet to which an external port number is specified, converts the external port number to an internal port number based on the port mapping table and transfers the internal port number to the LAN; a timer unit which counts the unoccupied time of the port after transferring a communications packet to which an external port number is specified; and a port management unit which checks whether the registered machine is present on the LAN and in case it is absent, deletes registration concerning the external port number from the port mapping table.

Abstract: A transmission apparatus for transmitting key operation information in a wireless signal form can avoid erroneous operation, even when a radio interference occurs between a transmission system and a reception system. A keyboard outputs a key make code when a key is depressed, and outputs a key break code when the key is released. Even when the keyboard is connected to a personal computer via a wireless signal, these key codes are transmitted utilizing the wireless signal. However, after the key make code is transmitted, if the key break code cannot be transmitted due to noise, then the personal computer cannot recognize that the relevant key is released. The transmission system (keyboard side) regularly transmits a fixed-term identification code (ID code) to the reception system (personal computer side).

Abstract: During a communication, when frame sync is lost in the receiver section of a spread spectrum communication apparatus, after the said sync is recovered, ID certification is practiced when the field intensity just before the loss is strong, or skipped when the said intensity is weak, and then the communication is resumed. Thus, the communication interrupt time due to the loss of sync is reduced.

Abstract: A radio apparatus using a limited channel scan mode is provided. In the limited channel scan mode, a parent unit scans for transmitting within a limited channel group determined on the basis of the last channel used, and a child unit intermittently scans for receiving within the same limited channel group. Since not all channels are scanned, the working time of the child unit during one scan period is shortened and the battery power is saved. When interference occurs during communication, the channel being used is switched and the channel group thereafter is thus also changed.