In the past, handlers often relied on collar bells to keep track of their dogs while in the field. They were usually used as a tool by upland hunters who worked only pointing breeds. Today, bells are still used extensively by handlers as a simple, inexpensive way to track valuable gun dogs. Different bells produce different tones, so handlers can distinguish between multiple dogs in the field.
While bells function well, many hunters and trainers today have replaced them with electronic beeper collars that can be programmed to function in many different modes. While their sound can be heard over a much greater distance and in much thicker cover than the traditional bells, their real advantage is that they indicate when your dog is on point.
Most electronic beeper units, such as the Tri-Tronics Accessory Beeper or the Innotek PB-500, allow the handler to choose the frequency at which the collar emits its "chirp," usually once every 5 or 10 seconds while the dog is moving and every second when he is on point or standing still. Most units also allow the handler to easily turn them on or off when they aren't needed.
Collar bells and electronic beepers have prevented the loss of numerous dogs that have wandered off or chased unwanted game into deep cover. For this reason, these tracking devices are used on pointing, flushing, and retrieving breeds. They allow you to always know where your dog is, what he is doing, and hopefully prevent his loss.
Photo from the book, "Just Setters".