Over 30 years of key and PBX undr my belt. The 81c and 61c that I maintained for a dozen years are gone. I now maintain 3 SBCs and 500 ports of analog to SIP gateways. We are in the process of phasing out our ISDN\PRIs in favor of SIP trunks. Once you understand the mechanism of how registrars work and the nomenclature used by each vendor to describe their related functions it becomes pretty easy. The data geeks that I work with are terrified of anything to do with dialtone or transcoding and forget installing an analog port on campus. For that they call out "Gandalf the Grey" (me). They are more concerned with packets not their contents. There are niches out there and I will second EV607797s opinion that more than a few SMBs are moving back to IP enabled TDM key hybrids. A Net+ or similar certification coupled with an Alta3 SIP certification will take you futher than the stack of TIE\Toshiba\Comdial\Nortel\Etc.... certifications that are yellowing in my attic.