The term shock collar is use to describe an electronic training aid developed to deliver an electrical signal through contact points attached to a dog collar. While similar systems are available for other animals, the most common and most controversial are the collars designed for domestic dogs. These electronic collars utilise the principle of psychological conditioning, whereby the dog is conditioned to link the undesired behaviour (barking, leaving the area etc.) with the pain induced by the collar. Controversy surrounds the use of the collars due to issues of long-term distress (Schilder & van der Borg 2004) and the ethics of training via the use of pain. Modern electronic collars are called remote electronic training collars by manufacturers and sometimes e-collars by users.