A data switch for network communications includes a first data port interface which supports at least one data port which transmits and receives data. The pre-set period of time for subsequent inhalations is adjusted depending on the time the person takes to stop inhaling after being signalled. A load capacitance of Cd is required to avoid voltage overshoot at the load and is provided by a capacitance of nCd arranged in parallel with each switch. The first and second gratings are formed by the holography method.