Digital button telephone system and extension terminal for the same

A digital key telephone system comprising a main unit connected to a communication network through an office line, accommodating a plurality of extension lines, and having at least a function of switching and connecting the office line to the plurality of extension lines or the extension lines to each other, and a plurality of extension terminals connected to the plurality of extension lines of said main unit, characterized in that

• at least one of the plurality of extension terminals comprises
• means for sending a request for knowing contents of an incoming call addressed to the extension terminal, and
• said main unit comprises
• call reception information notification control means for, when the request for knowing the contents of the incoming call is sent from the extension terminal where the incoming call waiting for call reception processing is present, supplying call reception information representing the contents of the incoming call waiting for call reception processing to the extension terminal of the request source in accordance with the request.

A digital key telephone system comprising a main unit connected to a communication network through an office line, accommodating a plurality of extension lines, and having at least a function of switching and connecting the office line to the plurality of extension lines or the extension lines to each other, a plurality of extension terminals connected to the plurality of extension lines of said main unit, and a computer connection interface added to at least one of the extension terminals, characterized in that

• said digital key telephone system comprises means for, when an operation mode change request to enter a computer telephony mode wherein the computer is connected to the office line arrives at the computer connection interface from a computer connected to the computer connection interface, transferring the change request to said main unit,
• said main unit comprises means for, when the mode change request is transferred from the computer connection interface, determining whether or not the main unit is compatible with the requested mode, and supplying a determination result to the computer connection interface which has transferred the mode change request, and
• the computer connection interface comprises means for performing mode change processing in response to the mode change request from the computer on the basis of the determination result supplied by said main unit after transfer of the mode change request.

A digital key telephone system comprising a main unit connected, through an office line, to a communication network having a function of transmitting a ringing signal including calling line identification information, accommodating a plurality of extension lines, and having at least a function of switching and connecting the office line to the plurality of extension lines or the extension line to each other, a plurality of extension terminals connected to the plurality of extension lines of said main unit, comprising:

• a plurality of storage means for storing information associated with the extension lines in correspondence with the respective extension lines;
• transfer processing means for, when a transfer request for transferring a call to a first extension line to a second extension line is set, transferring a call addressed to the first extension line, which is arriving through the office line, to the second extension line;
• and
• means for, when the second extension line of the transfer destination does not answer the call reception transfer processing by said transfer processing means, storing the calling line identification information in a storage buffer corresponding to the second extension line of the transfer destination, and for, when recalling the call transfer, storing the calling line identification information in each of a storage buffer corresponding to the first extension line of the transfer destination and the storage buffer corresponding to the second extension line of the transfer destination.