The present invention is typically embodied as a portable handheld unit that generates synchro signals for input into synchro motors and other synchro devices. A primary genre of inventive application is the testing of hardware and software in synchro systems. The inventive unit typically includes a numeric keypad, an LCD display, a microcontroller, a serial-to-parallel binary data converter, and at least one digital-to-synchro converter. The keypad and display are used to enter decimal data. The microcontroller converts the decimal data to serial binary data. The serial-to-parallel binary data converter converts the serial binary data to parallel binary data. The digital-to-synchro converter(s) convert(s) the parallel binary data to synchro analog data. Some inventive embodiments implement plural digital-to-synchro converters individually corresponding to channels for independently outputting synchro signals. Each channel can represent a specific type of synchro operation, e.g., ship rudder angle, ship speed, ship engine shaft revolution, ship heading, etc.