The letters actually refer to the connector shell size and are really independing of the number of pins. For example, a DB shell could have fewer than 25 pins. Some have two or even three heavy pins (one for power, 2 for return) and some signal pins. The reason the the 9-pin is designated DE is because it was developed after A, B, C, and D, sizes.
Drones are, in essence, flying autonomous vehicles. Pros and cons surrounding drones today might well foreshadow the debate over the development of self-driving cars. In the context of a strongly regulated aviation industry, "self-flying" drones pose a fresh challenge. How safe is it to fly drones in different environments? Should drones be required for visual line of sight – as are piloted airplanes? Join EE Times' Junko Yoshida as she moderates a panel of drone experts.