phone ▁and ▁light ▁are ▁attached . ▁A ▁wire ▁pendant ▁for ▁ho isting ▁and ▁lower ing ▁is ▁sh ack led ▁into ▁a ▁pad - ey e ▁on ▁top . ▁This ▁wire ▁is ▁also ▁used ▁for ▁retr ieving ▁the ▁chamber ▁in ▁case ▁of ▁emer gency . ▁The ▁forward ▁and ▁after ▁h atch es ▁of ▁American ▁sub mar ines ▁were ▁fitted ▁for ▁att aching ▁the ▁rescue ▁chamber . ▁They ▁have ▁a ▁flat ▁d ough nut ▁sh aped ▁plate ▁w eld ed ▁to ▁the ▁h atch ▁co aming ▁upon ▁which ▁the ▁bottom ▁of ▁the ▁chamber ▁rest s ▁and ▁a ▁b ail ▁over ▁the ▁center ▁of ▁the ▁h atch ▁to ▁which ▁the ▁ha ul ▁down ▁wire ▁must ▁be ▁attached ▁by ▁the ▁diver . ▁ ▁Lim itations ▁The ▁McC ann ▁bell ▁suff ers ▁severe ▁limitations ▁in ▁strong ▁curr ents ▁and ▁when ▁dealing ▁with ▁a ▁press ur ized ▁sub marine ▁or ▁one ▁lying ▁at ▁extreme ▁angles . ▁It ▁is ▁also ▁in cap able ▁of ▁function ing ▁below ▁. ▁The ▁US N ▁Sub marine ▁Res cue ▁Chamber ▁( Y RC ) ▁is ▁air ▁transport able ▁to ▁a ▁V essel ▁Of ▁O pport unity ▁( VO O ) ▁Mother ▁Sh ip ▁( M OS H IP ) ▁which ▁requires ▁little ▁modification ▁to ▁use ▁the ▁system . ▁Transfer ▁Under ▁Press ure ▁( T UP ) ▁to ▁and ▁from ▁press ur ized ▁environments ▁such ▁as ▁sub mar ines ▁or ▁hyper bar ic ▁ch amb ers ▁is ▁not ▁possible ▁with ▁this ▁system , ▁even ▁though ▁T UP ▁is ▁essential ▁where ▁being ▁subject ed ▁to ▁ambient