Squibs (or initiators) are electrical ignition devices that are used to activate various fire protection systems, including aircraft fire suppression systems. A squib typically consists of a small explosive charge that is detonated by an electrical current, which in turn ignites a pyrotechnic charge or opens a valve to discharge the fire suppressant.
In an aircraft fire suppression system, there may be two or more squibs per fire bottle, with each squib serving as a backup in case the other fails. These squibs are typically labeled as "Squib A" and "Squib B." The flight deck usually has a control panel that allows the crew to activate the fire suppression system, which then triggers one or both of the squibs.
The exact method of control depends on the specific design of the fire suppression system, but in general, the flight deck can choose which squib to use or use both squibs simultaneously. The choice of which squib to use may be based on factors such as the severity of the fire or the amount of suppressant remaining in the bottle.
In summary, there may be separate squibs A and B for each fire bottle, and the flight deck can usually select which squib(s) to use in an emergency. However, the exact configuration and control of the squibs will depend on the specific design of the aircraft's fire suppression system.