Echo is a common problem in long distance (propagation delay) telephony, and echo control devices are deployed to eliminate the effects of it. The call/bearer control entities 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 Recommendation defines the information and logical procedures employed within call/bearer control entities to optimise echo control device placement. The information elements and logic defined in this Recommendation are applicable to basic telephony calls, and to calls using supplementary services and Intelligent Networking features, in both narrow-band and broadband networks using circuit switched or packet bearer technology, and should be applied regardless of the particular signalling systems that convey information between the call/bearer control entities involved in a connection. This Recommendation is a revision of the ITU-T Rec. Q.115 (12/1999) and incorporates the contents of Implementor's Guide (12/2000) for ITU-T Rec. Q.115 (12/1999).