A communication apparatus for causing a display device to display information about communication received from another communication apparatus via a network, the communication apparatus comprising: an incoming call detection unit that detects an incoming call for starting the communication; an image output unit that is configured to output an image to the display device via a first communication path provided by an image transmission cable in order to cause the display device to display the information about communication; and a control unit that controls, via a second communication path provided by the network in response to the detection of the incoming call, a display function of the display device, the second communication path being different from the first communication path, wherein the control of the display function of the display device by the control unit enables the display device to display the information about communication, wherein the communication apparatus transmits information about an instruction to transmit state information to the display device in response to the detection of the incoming call, and receives state information, including information indicating whether a display function of the display device is operating or stopped, from the display device in response to the transmitted information about the instruction, wherein the communication apparatus transmits an instruction to enable the display function to the display device, when the received state information includes information indicating that the display function of the display device is stopped, wherein the communication apparatus sends via the network an inquiry about an input state of image signals to the display device, wherein the communication apparatus determines whether image signals are input into the display device based on information about the input state of image signals from the display device after sending the inquiry, wherein the communication apparatus sends via the network an instruction to display information to the display device, the information being for establishing connection of the image transmission cable to the communication apparatus, if the image signals are not input into the display device. an incoming call detection unit that detects an incoming call for starting the communication; an image output unit that is configured to output an image to the display device via a first communication path provided by an image transmission cable in order to cause the display device to display the information about communication; and a control unit that controls, via a second communication path provided by the network in response to the detection of the incoming call, a display function of the display device, the second communication path being different from the first communication path, wherein the control of the display function of the display device by the control unit enables the display device to display the information about communication, wherein the communication apparatus transmits information about an instruction to transmit state information to the display device in response to the detection of the incoming call, and receives state information, including information indicating whether a display function of the display device is operating or stopped, from the display device in response to the transmitted information about the instruction, wherein the communication apparatus transmits an instruction to enable the display function to the display device, when the received state information includes information indicating that the display function of the display device is stopped, wherein the communication apparatus sends via the network an inquiry about an input state of image signals to the display device, wherein the communication apparatus determines whether image signals are input into the display device based on information about the input state of image signals from the display device after sending the inquiry, wherein the communication apparatus sends via the network an instruction to display information to the display device, the information being for establishing connection of the image transmission cable to the communication apparatus, if the image signals are not input into the display device.