From my listening, Cleve medic unit rig radios IDs follow a logical numbering, first four digits being 1832 .. Then the next three digits are the unit number .. 001 for med 1, 004 for med 4 etc. Portables use same type numbering system 1832 then 101 or 201 for med 1, 10 or 204 for med 4 etc. That being said, yesterday I heard medic 20 but their Radio ID displayed as 1832017 .. So their might be inconsistencies or maybe some units using a spare.