The picture below depicts a
typical SMPF jumpering layout on our MDF (Main Distribution Frame). The circuit starts its journey at the particular block providing the CP's dial-tone (PSTN) .................. by using 'jumper wires' (Just a 2pr wire really), the Exchange Engineer then connects the dial-tone to the 'ADSL in' block of the ISP providing the broadband (ADSL).
By doing so, it means the dial-tone is sent to the ISP's broadband equipment (Sited somewhere in the Exchange), and is combined with the broadband circuit. Both dial-tone and broadband (PSTN & ADSL) then appear at the 'ADSL out' block on the MDF. From here, it is then 'jumpered' to the Bar/Pair which is basically the allocated pair of fuses feeding the EU's premises via the Cabinet.
If the circuit is an MPF (SKY, Tiscali, AOL, etc etc ....), both dial-tone and broadband are generated at the same block. However, as we (OR) need the ability to be able to test OLO's (Other Licensed Operators) circuits for faulting reasons, the circuit needs to be jumpered through our TAMS (Test Access Matrix System) to be able to achieve this.
So for this example ...... in the diagram below, substitute the ADSL in and out blocks, for TAMS in and out blocks.
I hope you can appreciate where the Exchange work is needed, whenever a change of circs takes place due to migration on ADSL services.