Keeping legacy networks up and running (and revenue bearing) is a
full on business. Nearly all of the equipment types are out of the original manufacturers (OEM) repair & support agreement and it takes a lot
of innovation to build the solutions to repair down to component level on legacy networks. In some cases the original manufacturers do not exist any more and neither do the spare components needed for the repairs.
However successful the innovations may be they all start with the idea. As many engineers will tell you, some of the best solutions were first realised on pieces of scrap paper or as in the above network diagram of a simplified Siemens Fastlink SHDSL testbed, on a piece of cleaning tissue.
Wikipedia defines innovation as;
"from the Latin word innovatus, which is the noun form of innovare "to renew or change," stemming from in-"into" + novus-"new"
This is a capture log of me using a Protocol Analyzer to watch the Ericsson DIAmuX connecting to the Local Exchange across an aggregate link using the V5.2 protocol.
You can see the Control protocol from the DIAmuX Access Network (AN) initiating the setup of the V5 link towards the Local Exchange (LE).
V5 is an older protocol and can be a bit of a nightmare when it doesn't want to work. If you have any problems drop me a line.
There is a very good V5 high level article on Wikipedia here and a good high level reference to CC Signalling here; Common Channel Signaling (CCS)
This is what a line card from the Siemens Fastlink system looks like.
Even today, telephony services such as Plain Old Telephone Services (POTS), which is the standard telephone service that most homes use and Integrated Services Digital Network (ISDN), remain an important source of income for service providers.
There are still many legacy systems in service that provide these services- such as Siemens Fastlink, an Access technology that provides POTS, ISDN, Leased Line and ADSL services across Europe.
Siemens describe Fastlink as a Multi-service Access System for Telephony, Data and Broadband Services.
Card product code: S42024-A1869-A1-09.
Card name: SUB162