Abstract: A portable device including a player capable of playing and recording digital data and a hard disk connected to the player for storing a relatively large capacity of digital data that can be transferred to and from the player. The hard disk is dedicated to the storage of digital data and program files for use with the player. The portable device can include a player and hard disk that are selectively detachable from one another. Alternatively, the player and hard drive can include an integrated construction wherein the player and the hard disk are incorporated into a single housing, preferably having a single circuit, such as a printed circuit board (PCB). In the integrated portable device, the typical electronics for managing the data on a hard drive are preferably integrated with the recording, playing, or displaying electronics. In addition, certain electronic components may be shared by the hard disk controller and player electronics, thus further reducing the cost and size of the portable device.

Abstract: A system for measuring body fat percentage is disclosed. The system relies upon the measurement of a subject's weight in two gases of different densities. The difference in weight, along with the difference in atmospheric density, is used to determine the subject's density. Implementing Archimedes' principle of binary mixtures, this figure is used to determine the proportion by weight of fat in the subject. The weight of the subject is measured with a precision balance. The density of the gas is determined with an ultrasonic probe that senses the change in sonic velocity, which is related to the density of the atmosphere.