A network switch for a packet-based data communication network, comprises a plurality of ports for the reception and transmission of data and means for establishing a database for controlling the passage of data between the ports. The delay trigger signal generator is connected to the external power source, to receive external power signals and generate a plurality of delay trigger signals. In preferred embodiments the calibrator is provided in gross excess. The magnetic device is connected to the track disc or is connected to the holding device and has at least two attracting modules, and each attracting module has an outer base and at least one magnet block.