The ACE 400i offers a 10 kHz operating system and greater detection depth with its large PROformance DD search coil. Its iron audio feature allows you to hear discriminated iron (normally silent) to avoid digging undesired flat iron objects such as bottle caps or washers. Other key features include 5 search modes, enhanced iron resolution control, non-motion electronic pinpointing and 8 levels of sensitivity/depth adjustment. Its digital target ID system, a numeric identification scale from 0 to 99, helps you more precisely identify a target metal’s conductivity. The ACE 400i includes an adjustable frequency to help eliminate or minimize interference caused by electrical sources or from other metal detectors.