The purpose of the magnet is to bend charge particle which traverse the magnet bore. Coming from the top, positively charged particles (positrons, protons, nuclei) curve in one direction and negatively charged particles (electrons, antiprotons, anti-nuclei) bend in the other. The degree to which they bend, that is the radius of curvature, depends on the "rigidity" of the particle, and the rigidity depends on the momentum and inversely on the charge-magnitude.

The tracker allows the measurement of this rigidity by registering the passage of a charged particle in each of the six planes. The strips on the "S" side of the wafer measure the "x" coordinate of the trajectory and the "K" strips measure the "y" coordinate. The "z" coordinate is known from the location of the tracker planes. In addition, the amount of energy deposited in each plane by the particle passage allows a determination of the charge magnitude of the particle.

The TOF counters also measure the energy deposition and so provide another measurement of the charge magnitude. By dividing the length of the trajectory between different layers by the difference in the signal times in those layers, the particle velocity can be determined. In addition, the coincidence of fast signals from counters in several layers is used to indicate when a particle has passed through the detector, and this indication is used to "trigger" the precise readout of all the detector elements.

Signals in the ACC counters indicate that a particle entered, or exited, the detector not though the TOF counters but through the magnet. As these particles cannot be precisely analyzed, signals from these counters are used to reject such particles.

The ATC supplements these measurements by providing a direct measurement of whether the particle velocity is above of below a threshold value.

The electronics has various functions. The trigger recognizes that a particle of interest has passed through the detector. Subdetector readout chains digitize the detector signals. The data acquisition system collates all the signals from the passage of this particle in to an event. The power system supplies the electronics and the detectors with the electricity required for them to operate. The heater system maintains the detector elements within operational temperature ranges. Monitoring and control electronics collect the various operational
parameters as well as operating the other electronics, either in response to the measured parameters or in response to commands. Data links interface the transmission of commands to, and parameters and event data from, the detector.

The LEPS and Skirt lessen the rate of spurious signals induced by low energy particles, especially electrons. The lowest portions of the experiment are protected by the material in the belly of the shuttle.

Away from the detector, support equipment constitutes the other end of these data links. Online software running on this equipment monitors the data, records it, and makes it available to the operators. The operators also use the online software on the support equipment to generate and transmit commands to the detector. Offline analysis works from these records to reconstruct the event and perform detailed physics analysis.