The 305, 310, 325 and 330 Series are high quality UHF camera-mount wireless systems that feature 188 User-Selectable frequencies displayed on an LCD screen to assure you of always finding a "free" channel. The series consists of the 305UPR, 310UDR, 325UPR and 330UPR On-Camera receivers, the 35BT Belt-Pack transmitter, the 35HT Handheld microphone/transmitter and the 35XT Plug-In transmitter.