Depending on the sea areas (A1-A4) a ship operates in, the GMDSS requirements will dictate what communications systems are carried.
It is possible to assemble a GMDSS compliant set-up from individual components but most ships are fitted with an integrated station supplied by one of the many specialist communications and navigation equipment providers.
An integrated station has several benefits over a custom assembled setup. Firstly, compatibility and connectivity is guaranteed and secondly only a single power supply connection is needed. As most integrated systems are supplied by major equipment suppliers, the issue of spare parts and repairs is likely to be much less of a problem with access to an established network of agents and repair centres.
Even with an integrated station there are some peripheral items that are installed elsewhere, the bridge fixed VHF being a good example. The systems are mostly quite compact and with the screens only needed to display text messages, there is no need for the large displays used elsewhere on the bridge for ECDIS and radar use.
As mentioned earlier, vessels are obliged to carry trained GMDSS operators who must supervise the use of the communications but the automated emergency DSC aspect of the equipment means that in a distress situation, all necessary information can be sent automatically at the touch of a single button by any crew member.