A memory controller, such as a SDRAM controller, controls the way in which data is retrieved, in order to make more efficient use of the bandwidth of the memory data bus. The adapter ring has a pair of interlocking hooks to allow the ring to be compressed to a first, compressed state, inserted into a wall niche and then relaxed to a second, rigid state. The data distributor card has a data port for coupling with a data stream. The transistors provide additional termination impedance to the differential IO pins. Therefore, a collision detecting device which can determine collision of an object with a vehicle accurately without being affected by the change of temperature can be obtained. The structure has a second stable position in which the SMA and metallized layers are flexed away from the cavity so that the contact pads are not in contact and form an open switch.