I applied online and after a few weeks I was called and told I could be interviewed on Friday (it was Wednesday). They arranged for me to fly in to Philadelphia from Austin on company expense. It was very short notice but I decided to go since the position seemed interesting.
The interviews were very informal and consisted of two parts: a "technical" interview and an HR interview. The "technical" interview was just a tour of the facility with small talk. The interviewer showed me some wireless communications devices and was interested in if I could keep up with the conversations. He never asked "interview questions," but rather it was up to me to demonstrate some knowledge.
The second part was an interview with HR. The interview was very straightforward, following the STARS format (look this up). He simply asked questions such as "talk about a time when you encountered a problem, and describe how you solved it."
That was actually entire interview process. They then told me they would let me know if I got the position (unfortunately I didn't).