Abstract: In a mobile telephone, it is planned to divide the functions usable by this mobile telephone into basic functions and comfort functions. It is planned that access to the comfort functions should be possible only if, in a test of comparison, an operator code stored in a memory of the mobile telephone corresponds to an operator code stored in a security circuit delivered by this operator when a purchaser purchases the mobile telephone, at the same time as he takes out a subscription with this operator. It is shown that, by acting in this way, it is possible to modulate the price of the subscription which may be attractive as well as the availability of the comfort functions of the mobile telephone. This can be done in such a way that economic profitability is ensured either by encouraging the user to keep his subscription with this operator or pay a fee to the operator a fee corresponding to an additional amount that absorbs the cost of the mobile telephone.