I've been a member of the Technical Communication program at UTSA for over twenty years--from before there actually was a Technical Commuication program! You'll find descriptions of the Technical Communication concentration and the required courses for Technical Communication majors elsewhere on the Communication site. Here I'll provide you some answers to frequently asked questions about the concentration.
It's a very broad field, to begin with. My usual, kneejerk answer is that it's the type of communication--written, verbal, and visual--that's done in technical industry, but that's a fairly bland answer. In general, technical communication deals with technical and scientific information, and in general, practitioners of technical communication specialize in taking that information and "translating" it for various audiences, from total novices to experts.
Our emphasis in the Communication Department is on the new media end of technical communication, which is the largest and fastest growing part of the field. We teach classes in writing for new media (Communication 3413), desktop publishing (Communication 3623), copyediting (Communication/English 2433, which includes eletronic editing), and a capstone course in digital media Communication 4723. We also teach special topics courses that cover various aspects of technical and electronic communication in greater depth.
Technical Communication majors would do well to choose their support work either in English (particularly the Professional Writing sequence) or in Computer Science.
Taking two concentrations is actually easier than you might think. You can use the courses you take for requirements in one concentration as electives in the other concentration; thus, the number of extra courses you have to take is less than it might seem. Moreover, combining two concentrations (e.g., technical communication and public relations or technical communication and electronic media) will give you extra background and qualify you for a wider range of employment or graduate programs. For more information about choosing two concentrations, consult the Communication Advisor.
The Communication program offers a "specialized area of study" in New Media and Information Design, which is comparable to a graduate program in technical communication.
In addition, there are several graduate programs available. The Society for Technical Communication has a partial listing of graduate programs on their Web site.
These questions are, of course, only a beginning. Please feel free to contact me for more information about the Technical Communication concentration.