Missing plane: Ship to tow 'black box' search device

An Australian Naval support vessel, ADV Ocean Shield, is being fitted with a US machine known as a "towed pinger locator" - as the search for missing flight MH370's "black box" devices is stepped up.

A TPL is pulled underwater behind a ship at slow speeds, and uses a hydrophone - highly sensitive listening equipment - to detect any ultrasonic signals - "pings" - from aircraft flight recorders.

The BBC's Jon Donnison, in Perth, has more details.