Detection device for monitoring at least one monitoring area by means of detection signals (38, 40), having at least one housing in which at least one detection transmitting device for transmitting detection signals (38, 40) is arranged, wherein the at least one housing has at least one transmission housing portion for transmitting detection signals (38, 40), wherein the detection device has at least one housing test device that can be used to test a functional state of at least one housing portion of the at least one housing and to generate at least one state signal when an actual functional state that is different from a reference functional state of the housing portion is identified, wherein the at least one housing test device has at least one test transmitting and receiving device that can be used to transmit electromagnetic test signals and to receive electromagnetic response signals and convert them into actual state variables that characterize an actual functional state of the at least one housing portion to be tested, wherein the at least one housing test device has at least one comparison means that can be used to compare at least one actual state variable and at least one predefined reference state variable, which characterizes a predefined reference functional state of the at least one housing portion to be tested, and to take the result of the comparison as a basis for generating at least one corresponding state signal, characterized in that the at least one housing test device has at least one test response device (34; 134) that is arranged on the at least one housing portion to be tested, wherein the test transmitting and receiving device can transmit electromagnetic test signals to the at least one test response device (34; 134) and can receive electromagnetic response signals that emanate from the at least one test response device (34; 134) as a response to electromagnetic test signals, wherein the at least one test response device (34; 134) has, or consists of, at least one antenna structure that is arranged directly on, and is connected to, the housing portion to be tested, with the result that changes in the functional state of the housing portion to be tested affect the response properties of the antenna structure. wherein the at least one housing has at least one transmission housing portion for transmitting detection signals (38, 40), wherein the detection device has at least one housing test device that can be used to test a functional state of at least one housing portion of the at least one housing and to generate at least one state signal when an actual functional state that is different from a reference functional state of the housing portion is identified, wherein the at least one housing test device has at least one test transmitting and receiving device that can be used to transmit electromagnetic test signals and to receive electromagnetic response signals and convert them into actual state variables that characterize an actual functional state of the at least one housing portion to be tested, wherein the at least one housing test device has at least one comparison means that can be used to compare at least one actual state variable and at least one predefined reference state variable, which characterizes a predefined reference functional state of the at least one housing portion to be tested, and to take the result of the comparison as a basis for generating at least one corresponding state signal, characterized in that the at least one housing test device has at least one test response device (34; 134) that is arranged on the at least one housing portion to be tested, wherein the test transmitting and receiving device can transmit electromagnetic test signals to the at least one test response device (34; 134) and can receive electromagnetic response signals that emanate from the at least one test response device (34; 134) as a response to electromagnetic test signals, wherein the at least one test response device (34; 134) has, or consists of, at least one antenna structure that is arranged directly on, and is connected to, the housing portion to be tested, with the result that changes in the functional state of the housing portion to be tested affect the response properties of the antenna structure.