The AML is manufactured exclusively by Subsurface Instruments. They do not publicize the details of how the instrument functions, but instead keep it as proprietary information. This keeps many people from trusting that the instrument functions at all, and that is understandable. However, for those of us who have actually experimented with it in the field on known utilities, I can state that it does function as advertised. -JAM
The AML uses 2 small red flashing lights to pinpoint the side of any smooth surface underground. So, walking across the ground, you can pinpoint both sides of a subsurface utility, such as a plastic pipe. This works in any type of soil, including clay soil.
This takes some practice to get acquainted with the instrument. You walk the search area – perpendicular to the utility line – the instrument pointed toward the ground – the lights flashing constantly – but when both lights remain on – then you are pointed at one side of the pipe – take another step forward – and the lights will remain on again – now pointing to the other side of the pipe.