This standard covers the transmission requirements for VGs. For the purposes of this standard, a 2 VG is considered to be a device that performs voice routing functions between: - Telephones; - Public and private networks; - Packet-based networks1. VGs include, but are not limited to: - Packet-based Enterprise equipment that is functionally equivalent to a TDM-based PBX; - Residential Gateways; - Voice-over-ADSL Integrated Access Device (IAD); 10 - Voice-over-Cable Multimedia Terminal Adaptor (MTA).