Process of access restriction to a telecommunications network, telecommunications system and unit for such a system

A telecommunication system comprising:

• a telecommunication network which stores predefined access codes corresponding to each of predefined criterions for each call;
• a mobile unit to place a call through said telecommunication network;
• wherein said telecommunication network restricts communication access of said mobile unit as a function of said predefined criterions;
• said mobile unit providing said telecommunication network with a mobile authentication code calculated by said mobile unit from inputs of a user of said mobile unit;
• and
• said telecommunication network calculating a network authentication code using said predefined access codes, and determining said communication access of said mobile unit based on a comparison of said mobile authentication code with said network authentication code and allowing said communication access if said comparison is favorable;
• wherein said telecommunication network cyclically determines said communication access during said call by cyclically requesting new mobile authentication codes from said mobile unit calculated from new input of said user, comparing said new mobile authentication codes with new network authentication codes, and shutting off said communication access if said new mobile authentication codes are not equal to said new network authentication codes.

A central telecommunication unit comprising:

• means for storing predefined access codes corresponding to each of predefined criterions for each call;
• means for restricting call placement by a mobile unit through a telecommunication network as a function of said predefined criterions;
• means for calculating a network authentication code using said predefined access codes, and
• determining means for determining communication access of said mobile unit based on a comparison of said network authentication code with mobile authentication codes calculated by said mobile unit from inputs of a user of said mobile unit and allowing said communication access if said comparison is favorable;
• wherein said determining means cyclically determines said communication access during a communication by cyclically requesting new mobile authentication codes from said mobile unit, said determining means comparing said new mobile authentication codes with said second authentication code during said communication, and said mobile unit calculating said new authentication codes in response to new inputs from said user of said mobile unit during said communication, said determining means shutting off said communication access if said new mobile authentication codes are not equal to said second authentication code.