This TSB covers issues associated with support of ECS from IP Telephony terminals connected to an Enterprise Network (EN). It describes new network architecture elements needed to support ECS@ and the functionality of those new elements. Many countries have similar ECS requirements. Portions of this document may be applicable in providing solutions for those requirements. This TSB addresses ECS calls placed from fixed@ mobile@ remote dial-in@ or wireless access VoIP terminals@ as shown in Figure 1. This figure also illustrates similar access scenarios for ECS calls placed directly through an ISP. Solutions contained within this TSB may apply to the non-enterprise environment as well. This TSB does not address scenarios for devices connected to VoIP networks through gateways. Many ECS support issues will require further investigation@ and are beyond the scope of this document. These include for example: ? Dialing procedures ? Call Reliability ? Call set-up delay ? Call queuing ? Calling feature override (e.g. call forwarding@ call waiting@ call conferencing@ caller ID suppression@ and do not disturb.) ? Access by persons with disabilities (e.g. TDD devices) ? Language-based call routing ? Use of a Private Safety Answering Point ? Transmission of supplementary call data (e.g. biometrics) Please note that using managed@ switched infrastructure described in this TSB does not necessarily provide a solution for the problem of remote access via VPN connectivity. It should be further noted that the determination of the appropriate PSAP to delivery of the ECS call is not detailed in this TSB. It also assumes that a sufficient number of local tandem ECS trunk connections exist to allow for a direct connection to the appropriate PSAP.