6 Characteristics
Clasification Society 2023 - Version 9.38
Statutory Documents - IMO Publications and Documents - International Codes - Alarms and Indicators - Code on Alarms and Indicators, 1995 Resolution A.830(19) - 6 Characteristics

6 Characteristics

  6.1 The emergency and primary alarms and call signals listed should have the audible and visual characteristics shown in the tables of this section. All other alarms, indicators and call signals should be clearly distinct from those listed in this section to the satisfaction of the Administration. These tables are not all-inclusive and other alarms may be added by the Administration in a manner consistent with this Code.

Table 6.1.1 Emergency alarms

Function IMO Instrument Audible Visual Remarks
Device Code Colour Symbol footnote
General emergency alarm
  • SOLAS III/50
  • SOLAS III/6.4

  • Whistle
  • Siren
  • Bell
  • Klaxon
  • Horn


  • 1.a,
  • 1.b
Green/White Muster stations for passengers.
Boat stations for crew.
Fire alarm Other than in machinery space
  • SOLAS II-2/40.4
  • SOLAS II-2/13
  • Bell
  • Klaxon
  • Siren
  • Horn


2, 1.b Red Fire stations for crew
In machinery space
  • SOLAS II-2/11.8
  • SOLAS II-2/14

  • Bell
  • Buzzer
  • Horn

  • 2,
  • 3.c,
  • 3.d
Red Horn, bell in machinery space, buzzer/bell elsewhere
Fire-extinguishing medium release alarm SOLAS II-2/5.1.6
  • Siren
  • Horn

2 Red Signal precedes release. Audible signal distinct from all others.
Power-operated sliding watertight door closing alarm SOLAS II-1/15.9.1;
for ships constructed on or after 1 February 1992, SOLAS II-1/15.7.1.6 and 15.8.2.
  • Horn
  • Klaxon
  • Bell

2
  • Red
  • Green

No symbol allocated Signal at door precedes and continues during door closing. At remote position: door open - red indicator, door closed - green indicator. On ships constructed on or after 1 February 1992, red indicator on navigating bridge flashes while door closes.
Note See table 6.2 for audible codes.

Table 6.1.2 Primary alarms

Function IMO Instrument Audible Visual Remarks
    Device Code Colour Symbol footnote  
Machinery alarm SOLAS II-1/51.1
  • Horn
  • Buzzer

3 Amber Horn in machinery space, buzzer elsewhere
Steering gear alarm
  • SOLAS II-1/29.5.2
  • SOLAS II-1/29.8.4
  • SOLAS II-1/29.12.2
  • SOLAS II-1/30.3

  • Horn
  • Buzzer
3 Amber Horn in machinery space, buzzer elsewhere
Control system fault alarm
  • SOLAS II-1/29.8.4
  • SOLAS II-1/49.5

  • Horn
  • Buzzer
3 Amber No symbol allocated Horn in machinery space, buzzer elsewhere
Bilge alarm SOLAS II-1/48
  • Horn
  • Buzzer

3 Amber Horn in machinery space, buzzer elsewhere
Engineers' alarm SOLAS II-1/38
  • Horn
  • Buzzer
3 Amber Horn/buzzer in engineers' corridors, buzzer in engineers' cabins
Personnel alarm Resolution A.481(XII), annex 2, paragraph 7.3
  • Horn
  • Buzzer

3 Amber Horn in machinery space, buzzer elsewhere
Fire detection alarm SOLAS II-2/12
  • Bell
  • Buzzer
  • Horn
2 Red  
SOLAS II-2/13 Ditto 2 Red Should automatically actuate fire alarm if not accepted in 2 minutes or less. Horn/bell in machinery space, buzzer/bell elsewhere.
SOLAS II-2/13-1 for ships constructed on or after 1 February 1992 Ditto 2 Red  
Alarm system fault alarm SOLAS II-1/51.2.2
  • Horn
  • Buzzer

3 Amber No symbol allocated Horn in machinery space, buzzer elsewhere
Cargo alarm IBC, BCH, IGC, GC
  • Horn
  • Buzzer
3 Amber No symbol allocated See tables 9.1.1 to 9.1.8 for IMO instrument references. Horn in machinery space, buzzer in engine control room, cargo control station and navigating bridge.
Gas detection alarm For chlorine gas
  • IGC 17.14.4.3
  • IGC 17.14.1.4
  • GC 17.12.5(d)(iii)
  • GC 17.12.5(a)(iv)


  • Siren
  • Horn
  • Bell

2 Red  
Except for chlorine gas
  • IGC 13.6.17.9
  • IGC 16.2.1.2
  • IGC 16.2.9
  • GC 13.6
  • GC 17.11
  • GC 16.2(b)
  • GC 16.10



  • Buzzer
  • Horn
3 Amber xxx Gas abbreviation may be indicated
Power-operated sliding watertight door fault alarm
  • SOLAS II-1/15.7.3
  • SOLAS II-1/15.7.8

for ships constructed on or after 1 February 1992
  • Horn
  • Buzzer

3 Amber No symbol allocated Horn in machinery space, buzzer elsewhere
Note See table 6.2 for audible codes.

Table 6.1.3 Call signals

Function IMO Instrument Audible Visual Remarks
Device Code Colour Symbol footnote
  Telephone SOLAS II-1/50
  • Horn
  • Buzzer
  • Bell


3.a White Horn/bell in machinery spaces and engineers' accommodation corridors; buzzer/bell in engine control room, on navigating bridge and in engineers' cabins
Engine-room telegraph SOLAS II-1/37
  • Horn
  • Bell
  • Buzzer
  • 2,
  • 3.a
White Horn/bell in machinery space, buzzer/bell in engine control room and on navigating bridge
Note See table 6.2 for audible codes.

Table 6.2 Audible alarm and call waveforms

Audible
code
Waveform Remarks
1.a General emergency alarm
1.b Specific codes per muster list
2 Continuous until cancelled or accepted
3.a Optional waveforms to provide distinction between alarms. To be used consistently for primary and secondary alarms. Pulse frequency between 0.5 Hz and 2.0 Hz
3.b
3.c
3.d

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