Radiodetection S18 Sonde (33 kHz) The Radiodetection S18 Sonde (33 kHz) is a compact transmitter designed for locating non-conductive underground utilities such as plastic pipes, sewer laterals, ducts, and conduits. Operating at 33 kHz , it delivers a strong, reliable signal that can be detected to depths of up to 14.5 ft (4.5 m) using compatible Radiodetection locators. Measuring just 0.70 in (18 mm) wide and 3.2 in (82 mm) long , the S18 easily fits onto push rods, drain rods and inspection cameras, making it ideal for confined or hard-to-access environments. Part Number: 10/SONDE-S18A-33 Key Features 33 kHz transmit frequency Locatable to 14.5 ft (4.5 m) Compact 18 mm diameter, 82 mm length Designed for non-metallic pipes and conduits Rugged, field-ready construction Ideal For Utility locating, sewer and drain inspection, CCTV surveys, and tracing plastic or non-metallic underground utilities.