The CCITT considering a) that there is a need to check the answerback of the called telex number [e.g. delivery from a telex-Teletex conversion facility (CF)/ or store and forward unit (SFU)]; b) that Recommendation F.60 defines a preferred structure for the telex answerback; c) that different forms of answerback exist; d) that Recommendation F.74 defines a structure for an answerback associated with an intermediate storage device.