Vevor 512Hz Sonde Rigid Drain Locator with 8/5" and 1/4-20" Connectors NewThe 512Hz sonde locator transmits a 512 Hz signal that can be picked up with any compatible locator, allowing users to pinpoint the transmitter's position underground. The maximum detection range of the transmitter is 25 feet in air, and 15 feet in cast iron (varies with ambient noise and interference). Two stainless steel adapters are provided so you can attach the transmitter to a drain cleaning cable or sewer camera to locate pipes underground.