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. Most carriers implemented either a soft or a hard ban on purchasing TDM-based gear on long-term capital budgets about two years ago, depending on whether or not they thought they could get VoIP-interface CPE gear for their value-added features/products. -- Nate Duehr nate@natetech.com -- http://www.piclist.com PIC/SX FAQ & list archive View/change your membership options at http://mailman.mit.edu/mailman/listinfo/piclist