Echo is a common problem in long distance (propagation delay) telephony, and echo control devices are deployed to eliminate the effects of it. The switching centres involved in a telephony connection must use consistent logical procedures to analyse the available information related to echo control requirements in order to optimize the locations at which echo control devices are provided in the connection. This ITU-T Recommendation defines the information and logical procedures employed within switching centres to optimize echo control device placement. The information elements and logic defined in this ITU-T Recommendation are applicable to basic telephony calls, and to calls using supplementary services and Intelligent Networking features, in both narrow-band and broadband networks, and should be applied regardless of the particular signalling systems that convey information between the switching centres involved in a connection.