The ACME Dog Whistle 'Silent' was the first of its kind. It is extremely well-made and a high-quality product that has been continuously improved since 1935. It produces frequencies that are not particularly audible to humans. However, dogs can hear them loud and clear. This allows for quiet and discreet communication and signaling to the dog. The frequency can be adjusted from 5400 to 12800 Hz using a smooth-threaded mechanism. Lower frequencies are suitable for long distances, while higher tones are optimal for close range. The chosen setting can be fixed once the dog has become accustomed to it or when working with multiple dogs. Depending on weather conditions and local circumstances, the whistle can be heard by the dog from up to 2 km away. The dog whistle comes with a cover cap connected by a chain and, of course, a ring.