An interbody spacer comprising a series of stacked walls connected by a common base, wherein the spacer collapses when pressed into an access delivery tube. With the elimination of the separator plate, a back pressure chamber is provided to resist the discharge pressure which will be directed against a rear face of the non-orbiting scroll. The number of usage blocks necessary to represent the number of logical blocks on the disk drive may then be determined and usage data may be stored in the usage blocks. When a radio receiving part receives a transmitting weight, a switching part outputs the received transmitting weight to multipliers.