Long-time software developer, systems internals, device drivers, embedded, Certified Palm Developer, worked on VoIP test and development tools (especially at the network levels - Ethernet (MAC), IP, TCP, SCTP, etc) - along with various SS7-to-Internet levels (M2PA, M2UA, M3UA, etc), now working on Android software.
And if that doesn't make your head spin, I'll start talking about assembly language...