Single & Twin Bell System

The Fathom Systems Emergency Bell Communicator System (EBC), or commonly referred to as  ‘Thru Water Communications’ (TWC), is designed to be installed on a Diving Support Vessel (DSV) or similar installation where one or more Submersible Decompression Chambers (SDCs) or Diving Bells are used for manned underwater diving operations.

The primary function of the system is to provide high quality back-up voice communications to and from the divers inside the bell in an emergency situation, where no conventional wired voice communications through the umbilical is achievable. Depending on the region of operation of the diving system, the system’s certifying authority and the operator’s policies, the EBC system may be a legal requirement for diving operations to proceed.  Fathom Systems recommend that reference is made to specific vessel/diving operating procedures for details.

The Emergency Bell Communicator system comprises the following main components:

  • Topside Transceiver Unit – located in the Dive control room, and used by Diving Supervisors to communicate with the Divers in the bell.
  • Topside Dunking Transducer – deployed through the vessel moonpool or over the side into the water.  This connects to the Topside Transceiver Unit.
  • External Bell Unit – a twin compartment oil filled and pressure compensated junction box mounted on the outside of the diving bell, containing the main electronic and power supply components for the bell system
  • Internal Bell Unit – the ‘Emergency Bell Communicator’ is the interface used by the Divers to communicate with supervisors at the surface and is accompanied by a ‘push to talk’ module, dual muff headset and penetrator disconnect junction box
  • Bell Transducer – mounted on the top of the bell, facing upwards
  • Bell Penetrator – an optional item available supplied in 1” NPT straight or right angle formats (smoothbore on request) incorporating 6 x individual STP, outboard PU sheathed cable terminated with Burton 55A1-2420 connector (length stipulated by client)

The system operates by using high frequency ultrasonic sound waves that are passed through the water between the bell and the surface vessel.  Communications are ‘half-duplex’ which means that only one person can talk at a time.  For this reason, a voice protocol where phrases are ended with the word “Over” is recommended (similar to the way 2-way radios are used). The system is generally tested at the start of every Dive or bell-run, and after this is left in the standby mode, ready for use should the need arise.  It is imperative that all Divers and Supervisors are familiar with the operation of the system.

This is a field proven product supplied globally for both new build and upgrade single and twin bell systems for a number of years.  It is often the preferred choice in the commercial diving industry with clarity of voice communications surpassing operator's expectations.