Must also fully understand the principles, methods and procedures applicable to the maintenance and repair of: Phase selective track circuits, Digital Transmission Systems, Real Time Computer Control and Monitoring Systems, Switch Machines, Way Side Signal Systems, Audio Track Circuit Systems, Carborne Control Systems, and Vehicle to wayside transmission systems. • Applicant must be able to understand and be proficient in the use of complex test equipment, including but not limited to Oscilloscopes, Digital Multi-Meters, Frequency Meters, Deviation Meters, Digital Probes, Semiconductor and logic Test Devices, and specialized diagnostic test equipment.