A radio local area network comprises a plurality of plug and play operating devices, such as TV, STB, VCR and PC, one of which devices functions as a central controller which sets up time division digital data links between the operating devices in response to activating a suitable manmachine interface, for example an infra-red TV remote controller. The testing method comprises the steps of providing a set of output test data to the communications system device being tested, and generating an output signal with the device in a manner that is responsive to the output test data. The frequency specific reach values indicating the number of unique viewing devices that were used to present the creative a specified number of times.