Method and apparatus for code matching the base and mobile unit of a cordless telephone set

A method of establishing mutually matching identification codes in the base unit and mobile unit of a cordless telephone set wherein the base unit is connected to an external telephone network and the mobile unit is physically replaceable on and off the base unit, the base unit and mobile unit each comprising memory means for storing an identification code therein and means for transmitting information over a communication channel between the base unit and the mobile unit;

• the base unit and the mobile unit each remaining in a stand-by state in which information cannot be transmitted over such communication channel and being switched by the base station to an operational state in which information can be transmitted over such communication channel when a call request is received by the base unit from the external telephone network or from the mobile unit and the identification code in the mobile unit matches the identification code in the base unit;
• such method being characterized in that each time the mobile unit is replaced on base unit the identification code stored in each of such units is modified by the base unit by the steps of:
• (a) switching the base unit and the mobile unit from the stand-by state to the operational state;
• (b) comparing the existing identification code stored in the memory means in the mobile unit with the existing identification code stored in the memory means in the base unit, and
• when such codes match, proceeding immediately to step (c);
• when such codes do not match, waiting a comparatively long time before proceeding to step (c);
• (c) replacing the identification code stored in the memory means in the base unit and in the memory means in the mobile unit with a new identification code which is common to both such units;
• and
• (e) switching the base unit and the mobile unit back to the stand-by state.