More than 30 years ago, electronic dog collars made their way into the dog-training scene. However, because the first generation of dog training collars were only capable of delivering one level of stimulation to the dog, they where appropriately nicknamed shock collars. Recognizing the limitations of the first generation of electric collars, manufacturers worked to refine their design. Within the last 5-10 year, the technology of dog training collars was replaced, giving the trainer the ability to select multiple levels of intensity from the transmitter. This single advancement combined with customer education has done more for the widespread acceptance of electronic collars than any other advancement with electric dog training collars.