The propagation of a feedback signal, such as a DQS signal generated in response to a read request in a Double Data Rate memory system, into a digital host system, such as an ASIC, is controlled by using delay tracking to compensate for variable IO delay. The packing tray includes a plurality of cell pockets, each cell pocket having a lowermost sump area with at least one flap door punched out but not removed from the sump area, providing a drainage opening from the cell. If the symmetrical antenna loops are in-phase state, the plurality of sawtooth-shaped regions consist of the plurality of n-shaped sections with the non-interlacing method; if the symmetrical antenna loops are oppositephase state, the plurality of sawtooth-shaped regions consist of the n-shaped sections with the interlacing method. A time interval retaining unit retains a time interval T for restoring the application to an executable state. The spacer is a metal wire, onto which bodies made of a mechanically resistive insulating material, which are provided with a hole, are threaded at specific intervals.