The blades that were installed on the chassis when the standby MM was once primary. The time of the last update can be obtained by querying rbistUpdateTimePrimary object. The blades are listed as a bitmap. The bitmap is a string containing a list of 1's and 0's that is as long as the number of blades supported. If a blade is installed in a bay, a 1 is present in the string in the position representing the bay ID as read from left to right. For example, if blades are installed in bays 1, 5, and 13, and 14 blades are supported, the string would look like '10001000000010'.