0 6 3 2 2 4 ) ▁and ▁was ▁incorpor ated ▁on ▁ 9 ▁April ▁ 1 9 9 7 . ▁The ▁trust ' s ▁activities ▁are ▁fund ed ▁by ▁the ▁ 3 ▁local ▁authorities ▁whose ▁constitu ents ▁the ▁sir ens ▁serve , ▁North ▁Som erset ▁Council , ▁Br istol ▁City ▁Council , ▁and ▁South ▁Gl ouc esters hire ▁Council , ▁and ▁from ▁don ations ▁from ▁the ▁organis ations ▁running ▁the ▁CO MA H ▁sites ▁themselves . ▁ ▁Sir ens ▁▁ ▁The ▁sir ens ▁themselves ▁are ▁mounted ▁on ▁dedicated ▁pol es ▁and ▁all ▁but ▁one ▁are ▁manufact ured ▁by ▁the ▁Federal ▁Sign al ▁Corporation . ▁Most ▁of ▁them ▁are ▁Federal ▁Sign al ▁Mod ul ators . ▁They ▁are ▁operated ▁via ▁radio ▁signal ▁from ▁a ▁control ▁system ▁at ▁Av on ▁and ▁Som erset ▁Police ▁Head quarters ▁in ▁Port is head . ▁ ▁Test ing ▁ ▁The ▁sir ens ▁are ▁tested ▁at ▁ 1 5 0 0 ▁on ▁the ▁ 3 rd ▁of ▁every ▁month . ▁The ▁test ▁compr ises ▁the ▁following : ▁▁▁ 3 ▁minutes ▁of ▁the ▁alert ▁warning ▁( a ▁continuous , ▁stepped , ▁rising ▁tone ) ▁▁ 1 ▁minute ▁of ▁silence ▁▁ 1 ▁minute ▁of ▁the ▁all ▁clear ▁sir en ▁( a ▁continuous ▁constant ▁tone ) ▁ ▁Local ▁volunte ers ▁monitor ▁the ▁sir ens ▁on ▁test ▁day . ▁ ▁References ▁ ▁External ▁links ▁▁ ▁Sever ns ide ▁Sir ens ▁Trust ▁- ▁the ▁char itable ▁organisation ▁responsible ▁for ▁running ▁the ▁system ▁ ▁Category : Warning ▁systems ▁Category : S ir ens ▁Category :