it uses optical technology so your every move is tracked with digital accuracy. congratulations to the author for yet another great book! when there's an opportunity to make something, i jump at it! the best things is for owners to learn how to command their dog, which is also cost-saving because they may not have to send other dogs to school by teaching them at home." alarm may be turned off or will silence automatically after 1 min. and i just want to say thank you again to you. 