2.12 Communications and relocation system

  2.12.1 The communication system should be arranged for direct two-way communication between the control stand and:

• diver in water
• diving bell
• each compartment of the chambers
• diving system handling positions
• dynamic positioning room
• bridge, ship's command centre or drilling floor.

  2.12.2 Alternative means of communication with divers in the surface compression chamber and diving bell should be available in emergency.

  2.12.3 Each surface compression chamber and diving bell should be connected to a speech unscrambler when used with gas systems, including helium.

  2.12.4 A self-contained through-water communication system should be provided for emergency communication with diving bells when operating under water.

  2.12.5 A diving bell should have an emergency locating device with a frequency of 37.5 kHz designed to assist personnel on the surface in establishing and maintaining contact with the submerged diving bell if the umbilical to the surface is severed. The device should include the following components:

• .1 Transponder

  • .1.1 The transponder should be provided with a pressure housing capable of operating to a depth of at least 200 m containing batteries and equipped with salt water activation contacts. The batteries should be of the readily available "alkaline" type and, if possible, be interchangeable with those of the diver and surface interrogator/receiver.

  • .1.2 The transponder should be designed to operate with the following characteristics:

    Common emergency reply frequency		37.5 kHz
    Individual interrogation frequencies:
    - Channel A		38.5 ± 0.05 kHz
    - Channel B		39.5 ± 0.05 kHz
    Receiver sensitivity		+15 dB referred to 1 μbar
    Minimum interrogation pulse width		4 ms
    Turnaround delay		125.7 ± 0.2 ms
    Reply frequency		37.5 ± 0.05 kHz
    Maximum interrogation rates:
    - more than 20% of battery life remaining		Once per second
    - less than 20% of battery life remaining		Once per 2 seconds
    Minimum transponder output power		85 dB referred to 1 μbar at 1 m
    Minimum transducer polar diagram		-6 dB at ± 135° solid angle, centred on the transponder vertical axis and transmitting towards the surface
    Minimum listening life in water		10 weeks
    Minimum battery life replying at 85 dB		5 days

• .2 Diver-held interrogator/receiver

  • .2.1 The interrogator/receiver should be provided with a pressure housing capable of operating to a depth of at least 200 m with pistol grip and compass. The front end should contain the directional hydrophone array and the rear end the three-digit LED display readout calibrated in metres. Controls should be provided for "on/off receiver gain" and "channel selection". The battery pack should be of the readily available "alkaline" type and, if possible, be interchangeable with that of the interrogator and transponder.

  • .2.2 The interrogator/receiver should be designed to operate with the following characteristics:

    Common emergency reply frequency		37.5 kHz
    Individual interrogation frequencies:
    - Channel A		38.5 kHz
    - Channel B		39.5 kHz
    Minimum transmitter output power		85 dB referred to 1 μbar at 1 m
    Transmit pulse		4 ms
    Directivity		±15°
    Capability to zero range on transponder
    Maximum detectable range		more than 500 m

  2.12.6 In addition to the communication systems referred to above, a standard bell emergency communication tapping code should be adopted, as given below, for use between persons in the bell and rescue divers.

A copy of this tapping code should be displayed inside and outside the bell and also in the dive control room.