7 5 5   M Hz ▁would ▁go ▁over ▁the ▁tr unk ed ▁system ▁on ▁an ▁assigned ▁talk ▁group . ▁ ▁In ▁conventional ▁government ▁systems , ▁cross ▁band ▁repe aters ▁are ▁sometimes ▁used ▁to ▁connect ▁two ▁ag encies ▁who ▁use ▁radio ▁systems ▁on ▁different ▁bands . ▁For ▁example , ▁a ▁fire ▁department ▁in ▁Colorado ▁was ▁on ▁a ▁ 4 6   M Hz ▁channel ▁while ▁a ▁police ▁department ▁was ▁on ▁a ▁ 1 5 4   M Hz ▁channel , ▁they ▁built ▁a ▁cross - band ▁repe ater ▁to ▁allow ▁communication ▁between ▁the ▁two ▁ag encies . ▁ ▁If ▁one ▁of ▁the ▁systems ▁is ▁simple x , ▁the ▁repe ater ▁must ▁have ▁logic ▁prevent ing ▁transmit ter ▁key ing ▁in ▁both ▁directions ▁at ▁the ▁same ▁time . ▁V oting ▁compar ators ▁with ▁a ▁transmit ter ▁key ing ▁matrix ▁are ▁sometimes ▁used ▁to ▁connect ▁in compatible ▁base ▁stations . ▁ ▁Historic ▁ ▁In ▁looking ▁at ▁records ▁of ▁old ▁systems , ▁examples ▁of ▁cross - band ▁commercial ▁systems ▁were ▁found ▁in ▁every ▁U . S . ▁radio ▁service ▁where ▁reg ulations ▁allowed ▁them . ▁In ▁California , ▁specific ▁systems ▁using ▁cross - band ▁repe aters ▁have ▁existed ▁at ▁least ▁since ▁the ▁ 1 9 6 0 s . ▁Historic ▁examples ▁of ▁cross - band ▁systems ▁include : ▁▁ ▁Sol ano ▁County ▁Fire , ▁( former ▁Fire ▁Radio ▁Service ): ▁ 4 6 . 2 4 0 ▁input ; ▁ 1 5 4 . 3 4 0 ▁output . ▁This ▁system ▁was ▁dis m ant led