A new cordless telephone is registered to an existing cordless telephone system by transmitting the product identification number of the new cordless telephone from the access unit of the system to the new cordless telephone, receiving the transmitted product identification number at the new cordless telephone and verifying that the transmitted product identification number is correctly received. In response to the verification, the system and telephone identification numbers of the new cordless telephone are transmitted from the access unit to the new cordless telephone and stored into an electrically erasable programmable read-only memory of this telephone to be used for establishing calls.