7D-Link DWR-512 User Manual
Section 2 - Installation
Connect a Telephone
The  RJ-11  jack  on  the  back  of  the  router  allows  you  to  connect  a  standard  analog 
telephone for voice calls.
Simply plug the phone cable into the RJ-11 jack.
You can then use your handset to dial out as you typically would with a standard landline 
phone.
Your attached phone will also ring for any incoming voice calls.
Note:  Calls made will be charged at a rate determined by your mobile service provider.