Has_many :through question

I have 3 models

Circuit
has_many :alarms
has_many :dacsports, :through => :alarms

Alarm
belongs_to :circuit
belongs_to :dacsport

Dacsport
has_many :alarms
has_many :circuits, :through => :alarms

I have the circuit -> dacsport relationship going.

How do I correlate the alarm data to either the circuit or the
dacsport?