If it's the hub losing connection then the broadband light (or ADSL, or internet, whatever it's labelled as) light on the hub will go out (or start flashing)
If it's your computer losing connection to the hub then the lights will stay the same on the hub and your computer will report a lost connection.
If it's the first one then it's probably an issue with either your phone cabling or filters in the house, or possibly a fault on the line
If it's the latter then you probably have something nearby causing interference to your wireless signal and changing the channel the hub operates on will probably solve it...
I'm assuming it's a home hub3 ???
http://btybb.custhelp...n-my-bt-home-hub-3%3F
If it's not then the instructions are broadly similar anyhow..