Mid-range trainers are designed to provide useful training at significantly lower cost and development time than those for full-capability (full-scale) trainers. Mid-range trainers are appropriate for use prior to development of full-scale trainers and as supplements to full-scale trainers. With a mid-range trainer, trainees may, for example, practice operational procedures, become familiar with system control locations and reaction times, and learn to recognize and handle system faults. This paper describes the B-52 OAS/CMC Part Task Trainer, detailing its function as both a conversion trainer to provide the highest level of simulated training while the full-range trainer is being developed, and as a "lead in" trainer before the student moves to the full-range device. Capabilities of the Part Task Trainer are explained. Cost effective aspects of dual use are discussed. Design features to provide lower initial cost and flexibility for future modification and expansion, use of minicomputers, off-the-shelf components, and modular structure are detailed.