A method of embedding auxiliary data in coefficients generated for a compressed data stream applies embedding rules to selected coefficients in different blocks to embed the data. One embodiment allows the player to select a pattern of wildcard symbols and use the selected pattern during a free spin bonus game. The data can describe a second user participating in the group transaction. As a result, heat-production is damped thereby preventing heat demagnetization of the permanent magnet. As an overtaking vehicle approaches in an adjacent lane, its approach is detected sequentially by the beams on that side of the vehicle. An elongated energy dissipating member extends horizontally within the cavity, and in one form, comprises a set of resilient cylindrical tubes of extruded plastics material with a smaller tube enclosed within a larger outer tube.