Universal Avionics Systems Corporation's Radio Tuning Unit (RTU) is a 2MCU box which provides the interface between the FMS displays and Collins ProLine II radios for true frequency management (Collins CSDB Interface). A single RTU allows dual FMS systems to be interfaced with up to eight radios through the Collins CTL control heads. The eight radios consist of the following: Three Comm, Two Nav, Two ADF (single or dual control heads), One Transponder. This frequency management is designed around the concept of providing an easy method of selecting, preselecting (4 frequencies) and viewing active channels of radios on board the flight deck. The CTL control heads and the FMS frequency management are interactive and require no manual switching for selection of one to the other.