Detector for locating warning grid placed over underground works, comprises receiver which detects electromagnetic radiation reflected by conductors in grid from incident transmitter radiation

摘要

Transmitter (5) uses shielded antenna (8) to send electromagnetic radiation towards warning grid (3) containing reflecting conductors whose length is adjusted to transmitter frequency and ground permittivity. To determine grid presence, receiver (6) with shielded antenna (9) receives reflected radiation from grid and compares it with transmitted radiation received over cable connection (7).