To connect a traditional voice T1 to the NetSapiens SNAPsolution platform you will need to procure a T1 SIP Gateway that is available from a variety of manufactures such as : Audiocodes, Sangoma, TelcoBridges.  The choice will likely be dependent upon your application and factors such as overall density/capacity and signaling protocols supported by the device and what is required by your application. 

From the SNAPsolution perspective, you will configure the Gateway as a 'Connection' in the NMS or SAS.