1. Field of the Invention
The present invention relates to an image communication device which transmits and receives image data and text data by using a call control protocol such as the Session Initiation Protocol (SIP).
2. Description of Related Art
Recently, communication devices, which carry out various data communications through an Internet Protocol (IP) network such as an IP telephone communication and an electronic mail communication, are becoming widespread. A proposal is made on a facsimile machine, which carries out a data communication for both voice data and image data. For example, a conventional facsimile machine includes an IP telephone communication function and an IP facsimile communication function based on the International Telecommunication Union-Telecommunications (ITU-T) recommendation T.38 and is capable of carrying out transmission and reception by an IP telephone communication and an IP facsimile communication at the same time. By transmitting image data of an original document by using the IP facsimile communication in place of a G3 facsimile communication, a voice communication can be carried out with a destination while transmitting the image data and the communication costs can be reduced.
However, since facsimile data transmitted to a destination through the IP network reaches the destination via many networks, there are fears that the facsimile data may be intercepted wrongfully by a communication device spoofing the true destination. Therefore, when the content of a transmission original document is a confidential document or the like which should not be learnt by a third party, even if a high communication cost is required, the G3 facsimile communication or the like, which transmits image data through a Public Switched Telephone Network (PSTN), had to be used.