External Extra Loud Siren An extra loud siren which can be fitted to the CAT1, CAT21 and CAT3 range of Acumen systems. ideal if the original alarm is buried under the seat which causes the siren noise to be reduced. Simple 2 wire fixing. Connects to the Yellow/Green wire of the alarm and a suitable ground point on the motorcycle. NOTE! Does not sound with the 'nudge' beeps of the alarms listed above - only on a full reaction.