The Australian Authorities, Air Chief Marshal Angus Houston, are announcing the Australian Defence Vessel, Ocean Shield, has found two distinct possibilities of independent return ping signals which align with the same frequency and identity as the Cockpit Voice Recorder and Flight Data Recorder of missing Malaysian flight MH-370.

Today, I can report some very encouraging information which has unfolded over the last 24 hours,” he told reporters in Perth

The initial signal was identified and held for two hours and twenty minutes as the Towed Pinger locator was dragged behind a 10 mile cable which suspends the sonar device at varying depths up to 3,000 meters.
The “ping signal” strengthened and weakened as both horizontal (distance) and vertical (depth) were travelled by the locator.    Two independent “ping signals” were identified.
According to U.S. authorities (in command of the locator) this solidifies a pattern consistent with both the flight data recorder (FDR) and cockpit voice recorder (CVR).  The sonar ‘ping’ signals were each recorded visually and acoustically. 

ADV Ocean Shield then turned around over the course of a 3 hour maneuver, redeployed the ping locator to a depth of 3,000 meters, and reacquired the ping signal(s) for an additional, and consecutive, 13 minutes.
While the Australian authorities are confident, they also express prudent caution as they continue to remind everyone that confirmation will only be possible with visible identification of wreckage. Efforts are underway to position a remote autonomous vehicle at the scene of the ping responses so that a visual search can be carried out using cameras.
The depth of the ping location at 4,500 meters is very challenging as that coincides with the absolute safe depth limit of the ROV.

Link to Australian Media – CLICK HERE 

A process of acoustic triangulation will now proceed with more passes of the area and attempts to reacquire the signal while towing the locator at varying compass headings.
Each of these passes takes a minimum of 8 to 10 hours from beginning to end so the process is slow and methodical.    The convergence point of each passe’s signal acquisition, intensity and location puts another line of clarity in the cross hairs upon the target below.
Once the location can be narrowed, then a remote unmanned sub will be deployed to visually search the defined area.