Switch-over in the specialization is allowed, in most universities, during the B.Tech course, but with certain criteria. Often, this criteria involve minimum GPA required, no availability of seats in that specialization, and because of being within or after the internal deadlines set by the university for stream change. Some institutions have a formal process and allow students to apply for the shift at the end of their first year or semester.
However, not all universities offer the flexibility to do so. And even if such switching is possible, there can be certain rules that might come in the way depending on course structure or too many students interested in a certain specialization. Specialization change rules vary with universities and should thus be sought directly from the relevant academic office when in B.Tech.