▁should ▁not ▁be ▁confused ▁with ▁the ▁block ▁ci pher ▁T iny ▁Enc ryption ▁Algorithm . ▁ ▁The ▁TE A ▁ci ph ers ▁have ▁different ▁avail ability ▁due ▁to ▁export ▁and ▁use ▁restrictions . ▁ ▁F ew ▁details ▁are ▁published ▁concerning ▁these ▁propriet ary ▁ci ph ers . ▁Ri ess ▁mentions ▁in ▁early ▁T ET RA ▁design ▁documents ▁that ▁encryption ▁should ▁be ▁done ▁with ▁a ▁stream ▁ci pher , ▁due ▁to ▁the ▁property ▁of ▁not ▁propag ating ▁transmission ▁errors . ▁Park inson ▁later ▁confir ms ▁this ▁and ▁explains ▁that ▁TE A ▁is ▁a ▁stream ▁ci pher ▁with ▁ 8 0 - bit ▁keys . ▁TE A 1 ▁and ▁TE A 4 ▁provide ▁basic ▁level ▁security , ▁and ▁are ▁meant ▁for ▁commercial ▁use . ▁The ▁TE A 2 ▁ci pher ▁is ▁restricted ▁to ▁European ▁public ▁safety ▁organis ations . ▁The ▁TE A 3 ▁ci pher ▁is ▁for ▁situations ▁where ▁TE A 2 ▁is ▁suitable ▁but ▁not ▁available . ▁ ▁Add itional ▁information ▁▁ ▁Terr est rial ▁Tr unk ed ▁Radio ▁( T ET RA ); ▁Vo ice ▁plus ▁Data ▁( V + D ); ▁Part ▁ 7 : ▁Security ▁ ▁Cell ▁selection ▁ ▁Cell ▁re - selection ▁( or ▁hand - over ) ▁in ▁images ▁▁ ▁This ▁first ▁representation ▁demonstr ates ▁where ▁the ▁slow ▁res elect ▁threshold ▁( S RT ), ▁the ▁fast ▁res elect ▁threshold ▁( F RT ), ▁and ▁propag ation ▁delay ▁exceed ▁parameters ▁are ▁most ▁likely ▁to ▁be . ▁These ▁are ▁represented ▁in ▁association ▁with ▁the ▁decay ing ▁radio ▁car rier ▁as