[Asterisk-Users] Outbound SIP Provider Nikotel Ringback

[Kevin]

Title: Huge silence breaks between Cisco 7960 phone & X-Lite

I hear no ring back tone when I place a call using Nikotel as my outbound provider to a PSTN telephone number.  When I call to a Vonage telephone number I get a ring back tone.  Any suggestions as to why I do not receive ring back tone when calling PSTN numbers?