The body of a detector is connected to a connection portion, a ten-key pad and a + 1 key are used to set the address, and a writing key is depressed to write the address on a memory. When a mode switch is set to an analog mode and then a test key is depressed, a test of the detector can be performed in such a manner that address information of the body of the detector is read and indicated through the connection portion. Furthermore, when a test cable is connected to a terminator of a circuit in the detector followed by switching the mode switch to a terminator side and depressing the test key, a test of the terminator can be performed. According to the present invention having the foregoing structure, a multiplicity of addresses can be set in a short time, satisfactory portability can be realized and a test of the detector and that of the terminator can be performed.