Method of controlling access to a door of an elevator system, with at least a first, a second, and a third communications unit for transmitting and receiving an identification code, an acknowledgement code, and an access code, wherein the method comprises the following steps: a) receiving the identification code with the second communications unit, wherein the second communications unit is a stationary terminal on a first floor, wherein the identification code is transmitted at a predetermined first transmission power from at least one first communications unit, wherein a user on the first floor has the first communications unit with him; b) receiving the identification code with the third communications unit, wherein the third communications unit is a stationary terminal on a second floor; c) checking the identification code by the second communications unit and by the third communications unit; d) simultaneously transmitting the acknowledgement code at a second transmission power that is lower than the first transmission power from the second communications unit and from the third communications unit to the first communications unit if the check of the identification code by the second communications unit and the check of the identification code by the third communications unit were successful, wherein the acknowledgement code transmitted from the second communications unit is receivable by the first communications unit, and wherein the acknowledgement code transmitted from the third communications unit is not receivable by the first communications unit due to the lower second transmission power; e) receiving the access code with the second communications unit from the first communications unit, wherein the first communications unit, after receipt of the acknowledgement code transmitted from the second communications unit, transmits the access code filed in a memory unit of the first communications unit; f) checking the access code by the second communications unit; and, g) freeing the access if the check of the access code was successful. a) receiving the identification code with the second communications unit, wherein the second communications unit is a stationary terminal on a first floor, wherein the identification code is transmitted at a predetermined first transmission power from at least one first communications unit, wherein a user on the first floor has the first communications unit with him; b) receiving the identification code with the third communications unit, wherein the third communications unit is a stationary terminal on a second floor; c) checking the identification code by the second communications unit and by the third communications unit; d) simultaneously transmitting the acknowledgement code at a second transmission power that is lower than the first transmission power from the second communications unit and from the third communications unit to the first communications unit if the check of the identification code by the second communications unit and the check of the identification code by the third communications unit were successful, wherein the acknowledgement code transmitted from the second communications unit is receivable by the first communications unit, and wherein the acknowledgement code transmitted from the third communications unit is not receivable by the first communications unit due to the lower second transmission power; e) receiving the access code with the second communications unit from the first communications unit, wherein the first communications unit, after receipt of the acknowledgement code transmitted from the second communications unit, transmits the access code filed in a memory unit of the first communications unit; f) checking the access code by the second communications unit; and, g) freeing the access if the check of the access code was successful.