ApplianX SIP Trunking Gateway is a TDM to SIP (VoIP) gateway, often installed within an enterprise or service centre. ApplianX SIP Trunking Gateway can support an internal TDM-based telecoms infrastructure (PBXs etc.), whilst providing access to either remote PSTN services provisioned over a public or managed IP network, or implementing replacement of a VPN using a public or private IP network for transport.