Transmitting on the 121.5 MHZ emergency distress homing frequency, the signal can also be picked up by SAR organisations and any other vessels with the correct equipment.

The signal can be pinpointed at sea level from 0.5 to three nautical miles, dependent on the height of the equipment and the sea state. Marine Rescue say a helicopter at 1000ft can pick up the signals from seven to 15 nautical miles and the range increases to more than 70 nautical miles to a fixed wing aircraft at 33,000 ft.

The company says the unit is designed to keep the rescue localised without activating global satellite systems.

The Sea Marshall range includes the PLB8-LR, with combined radio and electroluminescent flashing antenna, for sailors and fishermen. The PLB8-LD is for divers with a 100m depth rating. For the oil and gas industries there is the PLB8-IS, an intrinsic safe model.

The Sea Marshall PLB is patented and has full EU and US approvals. It has been featured on the BBC's Tomorrow's World, Sky Discovery Channel and the National Geographic Channel.

Marine Rescue says the Waveline Lifesaver MOB Safety Whistle was designed by search and rescue professionals.

It conforms to - and exceeds - US Coast Guard and SOLAS Regulations. The full 118 dB sound spectrum of the staccato whistle counteracts the blending effect of the noise of the wind and sea. For survival on the water and land and a useful crime prevention device.

Marine Rescue Co Tel: 070 1740 3421 Fax: 070 1740 3422 Email: info@marinerescue.co.uk Web: www.mrtbeacons.com