The CCITT considering (a) that telegraphy essentially involves the transmission of digital information; (b) that errors reflect either losses or invalid information; ？ that signals can be regenerated at several points along the lin (inter alia by multiplexers and/or switching exchanges). So that distortion is no longer the main criterion of performance; (d) that Recommendation F.10 recommends as an objective, for communications in the public telegram, telex and leased circuit services operated by Ci-unit start-stop equipment with a modulation speed of 50 bauds, a maximum error rate tolerance of 3 in 100000 alphabetic telegraph signals transmitted; ? that transmission equipment is increasingly based on digital systems such as R.100-Series Recommendations mu1 tiplexers; (d) that, since increasing use will be made of digital network, performance criteria should be consistent with those of Recommendation G.821.