I have a Discovery Electronics built Viper that was sold by Kellyco. The Viper is a Cobra II with a 10 segment LED intensity meter and a toggle switch that allows the choice of lighting only one LED or more than one. According to a Kellyco ad when they were selling the Vipers, one or more of the LED's will supposedly light when some deeper targets give a signal too weak for the electronics to give an audio response. They called it an "added depth component". I wouldn't bet on it adding any depth, but it gives the user a little help in determining how deep a target is. Kellyco started selling the Cobra II in 1995, and the Vipers in 1996 if I remember right, but they only sold the Viper for about three years.. The Viper I have goes an inch or so deeper than the A & S (The A & S is a Cobra II sold by a different company), but that's because I have the A & S ground balance set a little more positive than it should be so hot rocks won't give a response and have the Viper set slightly negative. The negative ground balance results in the Viper giving a double beep on hot rocks, but also added the extra depth.