An apparatus comprises a controller for remotely controlling an implantable device that is used to adjust a gastric band, and the controller transmits a telemetric signal to the implantable device. Some embodiments of the comparison circuit use a comparison unit that performs an initial comparison of addresses using a subset of the address bits. Data is moved in and out of the floating point register as integer data, and is converted into floating point format as needed. The ground plane is disposed on the other side of the substrate, and has a hollow portion corresponding to the central area of the ring microstrip line. This can save considerable time during engine build and maintenance. Each permanent magnet is formed of a pair of magnet pieces having a pair of magnetic pole-facing portions radially extending and magnetized so that poles of the same polarity face each other in a circumferential direction.