hey exvz,
Ref1: Digi Phone Sys
The traditional, old-school PBX (eg; ATT System-25, N.N.Meridian, etc)
Ref2: IPT:
Csco Call Manager, Avaya S8xx, etc.
The digi system is probably going be easier to get your arms around. As X-Vz, u know the difference between a 66-block and a RJ21/f cable, i'm sure. It might be a good start, as well, in terms of getting familiar with; auto attendants, hunt groups, call vectors, etc.
Learning IPT systems is a pretty logical progression as it builds on top of what u learn in programming digi systems. I have seen alot of committed ''phone guys'' morph into top-notch "phone/data guys". Be advised, there's much to know, in doing it the right way...you need to understand; udp, tcp, codecs, compression, mos, tftp, dhcp, segments, networks, servers, etc. Moving Fwd:, IPT is where it's at, as u know.
If u want to learn digi systems, generally speaking, I'd ask y u want to learn what's being phased out?
If u want to learn ipt systems, I can certainly see how it makes sense to get-down the basics, on a digi-system, then progress to ipt.
Avaya IP Office is for small office and Cisco CallManager Express works well there too. In the digi world, there's the Merlin Ledgend and other options like NEC, Panasonic. Not to sound harsh, but, if by chance u're not willing learn data, u probably can't fully capitalize on the resource investment made in learning a key system. And, if that's the case, perhaps grow the business in a different direction.
If u're ready to get into the data world, or not sure if u want to, a very good start might be the official CCNA book from Cisco Press. Start reading and see if it's something that fit's u.
Br,
XoverIP
Ixix CC, SWE, LCNCS-C, LNCS-OF ,3CSA, 3CNTS, 3CSE, NNCAS, NNCDS, ENA, ENA-PS, ENS, CCNA, CCDA, CCNP, CCDP