To dumb it down to a basic level , consider how a ‘regular’ broadband DV customer connects to the service , they plug a standard phone into the telephone port of the BT router , fundamentally that’s an ATA (analogue telephone adapter) , a 2wire 50v presentation to a domestic telephone instrument , the hub generates things such as local dialtone , ringing current etc , obviously the SH2 only needs to provide sufficient electrical current etc for pretty short length home wiring and phone cord .
This transitional product is in essence the exchange equipment provided is also an ATA , but needs to be sufficiently more ‘powerful’ to run considerably longer copper pair lines from the exchange to the customer address ….the exchange kit is not simply a a rack of SH2 routers with their ATA’s connected to the ‘telephone only’ customers local loop terminating at the customer wall socket , but for simplicity it can be considered like just like this , the exchange equipment is using BT’s 21CN ( think of this as the broadband access ) with an associated ATA equipment connected to the customer’s cable pair at the exchange , so instead of the phone cord being a few meters in length , it now effectively can be 100’s or 1000’s of meters in length , so the customer has no need for locally powered router , their ‘experience’ is identical to PSTN , in that they make no changes within their homes , with the caveat that the full national number needs to be used .
