The unique dual function MAC-51Bx receiver is designed to be used in conjunction with the transmitter for tracing buried cables, ferrous/nonferrous pipes, metallized warning tapes, and plastic pipes with tracers. Or it can be used alone to locate any object with a magnetic field water and gas valves, septic tank handles, manhole covers, etc. Featuring a switch that allows you to choose between the high frequency (82.3 KHz) and the low frequency (571 Hz), the MAC-51Bx lets you locate a complete break using the LO mode and then continue on to trace beyond the break in the HI mode or trace a metal pipe joined with non-conductive gaskets.