Abstract: The present invention provides test equipment (40, 42, 44, 46) for testing an aircraft oxygen system control device (30) comprising one or more detector signal inputs for receiving detector signals representative of one or more conditions of an aircraft gaseous oxygen system. The control device is configured to generate one or more control signals for controlling one or more oxygen system condition indicators based on the received one or more detector signals. The test equipment comprises a test signal switching module (40) having one or more test signal outputs for providing test signals to the one or more detector signal inputs. The switching module (40) further comprises switch means (48, 50, 52) for switching on and off the test signals. The present invention also provides a method of testing the control device (30) using the test equipment.