Safety sensor (1, 1a, 1b) for monitoring the operational safety of a system a) with at least one safety signal input (11, 12) for receiving an input safety signal which can have a first signal state or a second signal state, b) with at least one safety signal output (15, 16) for transmitting an output safety signal which can have the first signal state or the second signal state, c) with a control unit which is connected to the at least one safety signal input (11, 12) and to the at least one safety signal output (15, 16) and which is configured to detect an operational state of the system which may be a safe or an unsafe operational state and to transmit an output safety signal whose signal state (21, 22) signals the detected operational state on the at least one safety signal output (15, 16), d) wherein the first signal state signals a safe operational state of the system and is represented by a signal value from a first value range assigned to the first signal state, and the second signal state signals an unsafe operational state of the system and is represented by a signal value from a second value range which is assigned to the second signal state and which differs from the first value range, characterized in that e) the control unit is configured to impress additional data on the transmitted output safety signal in that the signal value of the transmitted output safety signal is changed within the limits of the value range (23, 24) which is assigned to the presently transmitted signal state (21, 22) of the output safety signal depending on the additional data, and/or f) the control unit is configured to impress additional data on the received input safety signal in that the signal value of the received input safety signal is changed within the limits of the value range (23, 24) which is assigned to the presently received signal state (21, 22) of the input safety signal depending on the additional data. a) with at least one safety signal input (11, 12) for receiving an input safety signal which can have a first signal state or a second signal state, b) with at least one safety signal output (15, 16) for transmitting an output safety signal which can have the first signal state or the second signal state, c) with a control unit which is connected to the at least one safety signal input (11, 12) and to the at least one safety signal output (15, 16) and which is configured to detect an operational state of the system which may be a safe or an unsafe operational state and to transmit an output safety signal whose signal state (21, 22) signals the detected operational state on the at least one safety signal output (15, 16), d) wherein the first signal state signals a safe operational state of the system and is represented by a signal value from a first value range assigned to the first signal state, and the second signal state signals an unsafe operational state of the system and is represented by a signal value from a second value range which is assigned to the second signal state and which differs from the first value range, characterized in that e) the control unit is configured to impress additional data on the transmitted output safety signal in that the signal value of the transmitted output safety signal is changed within the limits of the value range (23, 24) which is assigned to the presently transmitted signal state (21, 22) of the output safety signal depending on the additional data, and/or f) the control unit is configured to impress additional data on the received input safety signal in that the signal value of the received input safety signal is changed within the limits of the value range (23, 24) which is assigned to the presently received signal state (21, 22) of the input safety signal depending on the additional data.