An ‘isolation test’ involves connecting only a single device to your phone line at a particular time. For example, if you’re experiencing an issue with no dial tone on your phone line, you would be asked to connect only a single handset to your landline socket. This would need to be without any filters, adaptors, extension cables or other devices of any type. This includes disconnecting equipment from all other sockets in the premises using your ADSL line such as:
broadband 
