11. A hydrophone is a listening device-does it need more skill than ASDIC ? 12. ASDIC was effective only at low speeds.13. Hedgehog solved one of the most pressing problems, keeping ASDIC contact at short ranges. 14. It was expected from British work on ASDIC that other nations would develop something similar. 15. He afterwards worked in Fairlie, Scotland, doing research on ASDIC for the Admiralty. 16. Unable to see anything in the darkness, they dropped ASDIC and the was sunk. 17. Two more depth charges were dropped when a weak ASDIC contact was regained at 0045. 18. I don't think they would mention ASDIC by name because it was secret. 19. Hedgehog allowed the target to be attacked while within the usable range of the ASDIC equipment. 20. They also could not use asdic , as it frightened them and lead to protracted chases.
