Nate Duehr wrote: > On Nov 16, 2007, at 6:06 PM, Dave Lagzdin wrote: > >> On 16/11/2007, Nate Duehr wrote: >>> ... >>> made more sense for carriers to start to upgrade the core switching >>> and >>> turn it into packet-switched networks, than to throw out PSTN >>> switches >>> right away. Their depreciation cycles are 10 years or more on that >>> big >>> gear. >>> >> >> I think you are a few decades short there Nate, >> IIRC: A 4E is basically a souped up 1E which would have been >> installed in >> the 60's?/70's? > > The 4E's are the "stuff" that's being replaced in the core at most > carriers by VoIP. In most cases the 4E's are now "front-ends" for > VoIP switches... at least on a few carrier's networks. > > The newer 5E's and DMS-250's are the ones that are still (just barely) > still depreciating. They are being augmented by IP gateways however, > depending on whether the CPE equipment wants a traditional PSTN TDM/ > digital interface (T1, T3) or IP. A 4E is a long distance switch while a 5E is a local switch. I think that 5E's can support IP but don't quote me on that. I can't comment any further other to say that AT&T began replacing their 4E since the early/mid 90's when Lucent announced that no new software was being developed for the switches (just bug fixes). -- Linux Home Automation Neil Cherry ncherry@linuxha.com http://www.linuxha.com/ Main site http://linuxha.blogspot.com/ My HA Blog Author of: Linux Smart Homes For Dummies -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist