Abstract: A failsafe avionics interface unit serves as a protocol converter system for translating data for control purposes from a digital communication bus to an analog control channel as an upgrade or interface to an existing analog control system. The avionics interface unit includes digital interface bus logic, a digital data processor module, an analog interface, and a mode selection circuit. Data communicated over the digital interface bus is periodically translated into equivalent analog control signals. For safety purposes, the avionics interface unit ensures the integrity of the system by repetitively looping back or wrapping the digital equivalents of the analog output signals and comparing them to commanded digital control values. The protocol converter system additionally monitors communications over the digital data bus for data continuity.