tone, UK BS 5839-1 (fire alarm, railway crossing) 142 Alternating tone 146 Alternating tone, France NFS 32-001 (fire alarm) 1 Powerful electronic sounders Certified for hazardous area use. When human safety
tone, UK BS 5839-1 (fire alarm, railway crossing) 142 Alternating tone 146 Alternating tone, France NFS 32-001 (fire alarm) 1 Powerful electronic sounders Certified for hazardous area use. When human safety