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How Mercury IP Intercom is helping to keep communication lines between underground mines and the surface safe whatever the emergency

Mar 2012


The customer operates a number of large scale coal mines in Australia. Day to day communications are carried out using IS (Intrinsically Safe) handsets at various locations within the mines that allow calls to and from other handsets, an operator as well as calls to be made and received from external sources.

In normal operation this system works extremely well, however, with the inherent dangers found in mining operations the system must be equipped to deal with emergency situations as they happen. Critically important when responding to an emergency is the ability to keep the communications system open and available. The Mercury system guarantees this by providing the system operator with a ‘break lines’ key allowing for all external calls to be severed instantly and then re-established from the control room panel when the emergency is over.

The Challenge

Australia’s coal mining sector is critically important to the country’s power production and export sectors and as such this industry continues to explore ways to increase its efficiency, effectiveness and safety. Communications is a key element to all three of these aims, whether it is routine calls or in response to an emergency, quick, dependable contact between the surface and the personnel below surface is essential.

In normal operation the system needs to accommodate telephone calls from above ground to the underground locations and vice versa and from one location underground to any one of the other 30 locations. When an emergency strikes, the operator needs to be able to take control and immediately sever all incoming and outgoing external communications, preserving system bandwidth to deal in the most effective manner with the emergency as it develops. The ability to sever these lines prevents, for example, non emergency calls jamming the system which then blocks essential calls from being made.

In addition to these key elements the system must be scalable allowing for it to be expanded as the need grows; it should also be highly configurable allowing for settings such as the delay before auto operator connection to be defined.

The Solution

The solution provided by Trilogy for this application involves four of its Mercury Interface Units equipped with FXO and FXS telephony cards and a dedicated telephony switch controlling the various underground elements of the network. Above ground a control room equipped with a half length PCI card and virtual panel has overall administrative control of the system.

Each of the four MIUs accommodate eight IS phones supplied by the client and allows each one to be assigned an individual number through which external callers can direct dial. Other simple functionality provided by the system includes automated connection to the control room after 5 seconds of the handset being lifted, ability to call out to external lines and the ability to call any of the other thirty IS phones directly.

At the operator position the system can be configured and managed with the operator able to call any one of the thirty IS phones with a maximum of four at any one time or in an emergency use a ‘Break Lines’ key to instantly sever all of the connections running through the telephony switch to external lines. This allows optimal efficiency to be achieved with management of the communications prioritised according to the safety need. Once the emergency has finished, the control room operator can re-enable the ability to make and receive external calls from their virtual panel. 

The system is extremely flexibly in design and has already been expanded to include an additional eighteen users bringing the system total to 48. To accommodate these new users an additional two MIUs and a second telephony switch were installed, demonstrating the flexibility that means this system can meet the needs of any application. 


Key challenges


  • Interoperability – disparate communications devices need to communicate freely
  • Real Time Communications – information flow should be without delay
  • Reliability – critical applications require robust, proven solutions
  • Right tools for the job – intrinsically safe phones in hazardous environments where other options are not suitable



Key Features of the Trilogy solution

  • Full interoperability between all operator, IS phones and all incoming call type
  • Real-time two way one to one, calls are supported
  • Ability for Operator to sever all external connections instantly and then re-establish this functionality as necessary. Although
  • not used in this installation the system can be configured to allow this function to be arranged into a number of sub-groups
  • Mercury is a field proven, COTS product with business/mission critical installations around the globe


Equipment Used

  • Mercury Interface Unit with Telephone Expansion (FXO) and Telephone Interface (FXS) Boards fitted
  • Customer Supplied IS (intrinsically Safe) Phones
  • Telephone Line Switch


Other Applications of the Trilogy system

  • Petro-chemical, gas and nuclear installations around the world including Malaysia, China and the United Kingdom
  • Port Security in the United States of America
  • Missile ranges and tracking stations
  • Military training and simulation
  • Coverage extension of commercial and military air to ground networks




  • nteroperability – disparate communications devices need to communicate freely