Apparatus for use with metallic structures

1. Apparatus for connection to a transformer rectifier unit which is operable to output a DC current for cathodic protection of a metallic structure, the apparatus comprising:

a modulator unit connected to receive a DC output from a transformer rectifier unit, and arranged for connection to a metallic structure, wherein the modulator unit is operable to produce a modulated current which is applied to such a metallic structure when the apparatus is in use, such that the metallic structure is detectable by a wireless locating device, and wherein the modulator unit is operable to be controlled remotely.

2. Apparatus as claimed in claim 1 , wherein the modulated current has a modulation frequency of less than 1 Hz.

3. Apparatus as claimed in claim 1 , wherein the modulator unit is operable to be controlled remotely using a wide area network, local area network or internet connection.

4. Apparatus as claimed in claim 1 , wherein the modulator unit is operable to be controlled remotely using a wireless controller.

5. Apparatus as claimed in claim 1 , wherein the modulator unit is operable to be controlled remotely using a mobile telephone.

6. Apparatus as claimed in claim 1 , wherein the modulator unit is operable to generate an interruption pattern to the DC output from the transformer rectifier unit.

7. Apparatus as claimed in claim 1 , further comprising a remote monitor unit operable to monitor operation of the transformer rectifier unit and such cathodic protection.

8. Apparatus as claimed in claim 7 , wherein the remote monitor unit is operable to generate alarms and status reports relating to the transformer rectifier unit and such cathodic protection.

9. Apparatus as claimed in claim 8 , wherein the remote monitor unit is operable to send such alarms and status reports wirelessly or via wired means to a control centre or monitoring station.

10. Apparatus as claimed in claim 7 , wherein the remote monitor unit is integral with the modulator.

11. Apparatus as claimed in claim 1 , wherein the modulated current has a modulation frequency of at least 1 Hz.

12. A method of detecting a buried metallic structure, the method comprising connecting a transformer rectifier unit to a buried metallic structure, supplying a DC current to the metallic structure to provide cathodic protection for the structure, modulating the DC current to provide a modulated current, and detecting the modulated DC current using a wireless locating device.

13. A method as claimed in claim 12 , wherein the modulated DC current has a modulation frequency of less than 1 Hz.

14. A method as claimed in claim 12 , being controlled remotely using a wide area network, local area network or internet connection.

15. A method as claimed in claim 12 , being controlled remotely using a wireless controller.

16. A method as claimed in claim 15 , wherein wireless controller is a mobile telephone.

17. A method as claimed in claim 12 , further comprising remotely monitoring operation of the transformer rectifier unit.

18. A method as claimed in claim 17 , further comprising generating alarms and status reports relating to the transformer rectifier unit and such cathodic protection.

19. A method as claimed in claim 18 , further comprising sending such alarms and status reports wirelessly or via wired means to a control centre or monitoring station.

20. A method as claimed in claim 12 , wherein the modulated current has a modulation frequency of at least 1 Hz.

21. Apparatus for connection to a metallic structure, the apparatus comprising:

a transformer rectifier unit operable to output a DC current for cathodic protection of a metallic structure;

a modulator unit connected to receive a DC output from the transformer rectifier unit, and arranged for connection to a metallic structure, wherein the modulator unit is operable to produce a modulated current which is applied to such a metallic structure when the apparatus is in use, such that the metallic structure is detectable by a wireless locating device, and wherein the modulator unit is operable to be controlled remotely.

22. Apparatus as claimed in claim 21 , wherein the modulated current has a modulation frequency of less than 1 Hz.

23. Apparatus as claimed in claim 21 , wherein the modulator unit is operable to be controlled remotely using a wide area network, local area network or internet connection.

24. Apparatus as claimed in claim 21 , wherein the modulator unit is operable to be controlled remotely using a wireless controller.

25. Apparatus as claimed in claim 21 , wherein the modulator unit is operable to be controlled remotely using a mobile telephone.

26. Apparatus as claimed in claim 21 , wherein the modulator unit is operable to generate an interruption pattern to the DC output from the transformer rectifier unit.

27. Apparatus as claimed claim 21 , further comprising a remote monitor unit operable to monitor operation of the transformer rectifier unit and such cathodic protection.

28. Apparatus as claimed in claim 27 , wherein the remote monitor unit is operable to generate alarms and status reports relating to the transformer rectifier unit and such cathodic protection.

29. Apparatus as claimed in claim 28 , wherein the remote monitor unit is operable to send such alarms and status reports wirelessly or via wired means to a control centre or monitoring station.

30. Apparatus as claimed in claim 27 , wherein the remote monitor unit is integral with the modulator.

31. Apparatus as claimed in claim 21 , wherein the modulated current has a modulation frequency of at least 1 Hz.