This digital ultrasonic collar operates all High Tech Pet Power Pet electronic pet doors and Sound Barrier and Yard Barrier sonic fences. Using all digital circuitry, this state of the art design provides a stronger signal and maintains better accuracy over all temperature ranges. It includes a specially designed B3V1A battery which lasts about 3 months and prevents damage to the circuitry if the battery is accidentally installed incorrectly. With a fully enclosed ultrasonic speaker, the MS-4 is water-resistant and rugged. It\’s perfect for the pet who likes to do some serious \”ruffhousing\”. While we don\’t recommend you let your pooch take it for a dip in the pool, our new MS-4 is fully immersible for short periods of time and will continue to work even when wet. It will stand up to heavy rain showers and is perfect for dogs who love to play in the snow. The enclosed transducer (speaker) is much more robust than conventional open air transducers and will stand up to far more abuse from your pet. Small and lightweight, one size fits all dogs and cats. Comes with an attractive and tough 27 inch nylon strap.