Returning to IFC Section 907, we see that 907.2.1 addresses assembly occupancies, stating that a manual fire alarm system is required if the Group A portion of the building exceeds 300 people or ...

A fire alarm system consists of a number of devices working together to detect and alert people through visual and audio signals whenever smoke or fire is present. These alarm signals may be activated ...

Group B fire alarm requirements can be found in IFC 907.2.2. This section is similar to the 907.2.1 requirements for Group A “Assembly” occupancies but has an added condition for multiple floors.