<P> Coding refers to the pattern or tones a notification appliance sounds in and is controlled either by the panel or by setting jumpers or DIP switches on the notification appliances . The majority of audible notification appliances installed prior to 1996 produced a steady sound for evacuation . In general , no common standard at that time mandated any particular tone , or pattern for audible fire alarm evacuation signals . While less common than a steady sound , differing signaling methods were used for the same purpose . These are named with respect to their distinctive structure and include , March Time ( usually 120 pulses per minute but sometimes at 90 pulses or 20 pulses per minute , depending on the panel ) , Hi - Lo ( two different tones that alternate ) , Slow - Whoop ( slow rising sweep upwards in tone ) among others . Today these methods are confined to applications intended to trigger a response other than evacuation alone . In 1996 , the ANSI and the NFPA recommended a standard evacuation pattern to eliminate confusion . The pattern is uniform without regard to the sound used . This pattern , which is also used for smoke alarms , is named the Temporal - Three alarm signal , often referred to as `` T - 3 '' ( ISO 8201 and ANSI / ASA S3. 41 Temporal Pattern ) and produces an interrupted four count ( three half second pulses , followed by a one and one half second pause , repeated for a minimum of 180 seconds ) . CO ( carbon monoxide ) detectors are specified to use a similar pattern using four pulses of tone ( often referred to as T4 ) . </P>
<P> Coding refers to the pattern or tones a notification appliance sounds in and is controlled either by the panel or by setting jumpers or DIP switches on the notification appliances . The majority of audible notification appliances installed prior to 1996 produced a steady sound for evacuation . In general , no common standard at that time mandated any particular tone , or pattern for audible fire alarm evacuation signals . While less common than a steady sound , differing signaling methods were used for the same purpose . These are named with respect to their distinctive structure and include , March Time ( usually 120 pulses per minute but sometimes at 90 pulses or 20 pulses per minute , depending on the panel ) , Hi - Lo ( two different tones that alternate ) , Slow - Whoop ( slow rising sweep upwards in tone ) among others . Today these methods are confined to applications intended to trigger a response other than evacuation alone . In 1996 , the ANSI and the NFPA recommended a standard evacuation pattern to eliminate confusion . The pattern is uniform without regard to the sound used . This pattern , which is also used for smoke alarms , is named the Temporal - Three alarm signal , often referred to as `` T - 3 '' ( ISO 8201 and ANSI / ASA S3. 41 Temporal Pattern ) and produces an interrupted four count ( three half second pulses , followed by a one and one half second pause , repeated for a minimum of 180 seconds ) . CO ( carbon monoxide ) detectors are specified to use a similar pattern using four pulses of tone ( often referred to as T4 ) . </P>
what is the intensity of a fire alarm that has a sound level of 120 decibels
what is the intensity of a fire alarm that has a sound level of 120 decibels
March Time
March Time