Portable Sound Source III, model 1-03040-01, is a signal beacon designed for use by children who are blind or have low vision in orientation and mobility (O&M) training and playground games. The beacon produces an audio tone that provides directional cues. The beeping tone has a rate of 36 to 360 pulses per minute, with a pitch of 600 hertz to 1200 hertz. It can be used for teaching sound location skills or for marking locations in playground games. The unit has a large built-in speaker and a handle for carrying, and comes with instructions in print. POWER: Uses four D batteries (included). DIMENSIONS (HxLxW): 8 x 9 x 3.5 inches. WEIGHT: Approximately 6 pounds.