▁known ▁as ▁Trans - Europe an ▁Tr unk ed ▁Radio ), ▁a ▁European ▁standard ▁for ▁a ▁tr unk ed ▁radio ▁system , ▁is ▁a ▁professional ▁mobile ▁radio ▁and ▁two - way ▁trans ce iver ▁specification . ▁T ET RA ▁was ▁specifically ▁designed ▁for ▁use ▁by ▁government ▁ag encies , ▁emer gency ▁services , ▁( pol ice ▁forces , ▁fire ▁depart ments , ▁amb ul ance ) ▁for ▁public ▁safety ▁networks , ▁rail ▁transport ▁staff ▁for ▁train ▁rad ios , ▁transport ▁services ▁and ▁the ▁military . ▁T ET RA ▁is ▁the ▁European ▁version ▁of ▁tr unk ed ▁radio , ▁similar ▁to ▁Project ▁ 2 5 . ▁ ▁T ET RA ▁is ▁a ▁European ▁Tele communic ations ▁Stand ards ▁Institute ▁( ET SI ) ▁standard , ▁first ▁version ▁published ▁ 1 9 9 5 ; ▁it ▁is ▁mentioned ▁by ▁the ▁European ▁Radio communic ations ▁Committee ▁( ER C ). ▁ ▁Description ▁ ▁T ET RA ▁uses ▁time - div ision ▁multiple ▁access ▁( TD MA ) ▁with ▁four ▁user ▁channels ▁on ▁one ▁radio ▁car rier ▁and ▁ 2 5   k Hz ▁spacing ▁between ▁carri ers . ▁Both ▁point - to - point ▁and ▁point - to - multip oint ▁transfer ▁can ▁be ▁used . ▁Digital ▁data ▁transmission ▁is ▁also ▁included ▁in ▁the ▁standard ▁though ▁at ▁a ▁low ▁data ▁rate . ▁ ▁T ET RA ▁Mobile ▁St ations ▁( MS ) ▁can ▁communicate ▁direct - mode ▁operation ▁( D MO ) ▁or ▁using ▁tr unk ed - mode ▁operation ▁( T MO ) ▁using ▁switching