Peter , there are 2 bottles for each engine (located in the pylons fwd and aft of the round access panels you can see).
Each bottle has one squib.
Press the left switch (AGENT 1) and Bottle 1's squib fires.
Press the right switch (AGENT 2) and Bottle 2's squib fires.
Both bottles share a common discharge pipe.
Same system for the CFM or IAE engine.
