Dial-up on an ADSL enabled line
After a bit on confirmation of something here...
Our Bursary has a telephone line that doesn't go through the school PBX, but it connected directly to the POTS network. They currently use this with a dial-up modem to connect to our Barclays business banking. We also have access to the newer Internet banking system that works through a browser, but for various reasons that I won't go into, they still need the dial-up.
I want to co-opt the line to install a backup ADSL connection into the school. I know from my own experience that even when ADSL is installed, you can still make a dial-up connection through the voice part of the line (even if it's a bit slower). However, given the perceived importance of the dial-up, I'm loathe to just blunder ahead without being sure.
To that end, I've stuck an ADSL filter on the line already to test the dial-up with the line frequency filtering in place, before ADSL is provisioned. The dial-up has been tested successfully with the filter in place.
My question is this: is this a valid test, or is there something I'm forgetting that could cause problems once the line is actually ADSL enabled?