According to rule 33(a) of the COLREG 1972, a vessel of 20 meters in length or more shall be provided with a bell and a vessel of 100 meters or more shall in addition be provided with a gong. The sound pressure level at 1 m distance shall be at least 110 dB,
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| ZÖLLNER Electronic Bell and Gong System ZBG110 || with 10+SGA |
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| ZÖLLNER Manual Glocke 300 M and Gong 500 M | |
| – as devices by themselves and as complement to the electronic system – | |
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| ZÖLLNER Electro-Mechanical Bell and Gong System 350EL/500 EL | |
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| ZÖLLNER Manoeuver Signal Lamp||with LED |