Exchanging system and method of establishing data call thereof

An exchanging system in which data transfers are conducted between a plurality of exchange offices connected to each other by a signalling line such that data is transferred between file means including files associated with the respective exchange offices and each of said exchange offices, comprising:

• user process means for outputting an input/output request to a file of a particular exchange office of a user,
• input/output control means operative in response to the input/output request to a file included in said file means of a particular exchange office received from said user process means for outputting an access request to an exchanging system of another particular communicating exchange office to which the file means including said file belongs;
• and
• signal connection means, operative based on the access request to the particular exchange office received from said input/output control means, for outputting signal connection control information to said another particular exchange office, thereby establishing a connection to said another particular exchange office to which the file belongs.