<p>A communication device (100) is connected with an external device via a network. The communication device is equipped with a network port (105) for connecting to the network, a variable resistance unit (106) which is connected to the network port (105) to be able to detect a resistance value from the external device and is capable of changing the resistance value, and a control unit (107) which controls the variable resistance unit (106) to change to a resistance value according to the operating state of the communication device (100).</p>
