Method for controlling a terminal equipment coupled to an integrated services digital network and a terminal equipment based on the same

A terminal equipment coupled, through a single communication line, to an integrated services digital network (ISDN) handling data in digital form, comprising:

• ISDN interface means, coupled to said ISDN, for executing a transmission control procedure related to up to layer 3 of an ISDN structured architecture.
• discerning means for discerning whether a message supplied from said ISDN is received through said ISDN interface means, said message being used at the time of setting up a call;
• first determining means, operatively coupled to said discerning means, for determining, each time said message is received, as to whether or not said message includes information on whether a different terminal equipment which said terminal equipment communicates with is a terminal coupled to either an ISDN or an analog network other than said ISDN, said analog network being coupled to said ISDN;
• second determining means, operatively coupled to said first determining means, for determining whether the different terminal equipment is a terminal coupled to said ISDN or said analog network other than the ISDN;
• first control means, coupled to said second determining means, for executing a first communication control suitable for exchanging data with the different terminal equipment through said ISDN, when the different terminal equipment is determined to be a terminal coupled to the ISDN by referring to said information included in said message;
• second control means, coupled to said second determining means, for executing a second communication control suitable for exchanging data with the different terminal equipment through said ISDN and said analog network connected thereto, when the different terminal equipment is determined to be a terminal coupled to said analog network other than said ISDN by referring to said information included in said message;
• and
• switching means for selectively connecting one of said first control means and second control means to said ISDN interface means, said switching means being controlled based on the determination result in said second determining means.