Integrate VoIP on our FR network

Hi to all,

I’m planning to integrate VoIP on our Frame Relay Network, currently my FR network uses direct mode. My FR setup is nodal that is branch offices (64kbps) connected to our regional offices (256kbps) and regional offices to our head office (E1). Is it possible for me to integrate VoIP from my exixting FR network (WAN)? What equipment and devices will I need? Is anyone can HELP? Thanks in advance…