Setup with a Viking PA-2A for paging with Megapath's Hosted VoIP system.Here is how we used it:Cisco SPA 122 Line 1 - Phone Line In on the RAD-1A.Port 1 on RAD-1A to Port 6 on PA-2A.Port 2 on RAD-1A to Port 5 on RAD-1A.Port 6 on RAD-1A to Port 5 on PA-2A.works great!I do a lot of International phone calls, but billing was killing me. got this device and hooked it up to a dedicated phone line at home and to my VOIP modem. Now all I have to do to call overseas is call home (regular cell phone plan), punch in a code and dial overseas. Great way to save money.Works as described. Installed them in IT closets to our FXS ports and connected to the PA system at two locations.Works as expected. Had some issues setting it up, but phone support from the OEM is stellar.we've used this device and the prior model for over 10 years on dozens of projects.Never had a failure. Very solid device.used to replace a failed unit and works greatOur new VOIP phone system would not work with our existing paging system. After buying this product everything worked perfectly!