ÿWPCL ûÿ2BJ|xÐ ` ÐÐÌÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿH øÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÿÌÐÐ °°°è ÐÑ Âx„|ü@Ž ÑÐ Å°6Ø'°6Ø'Å Ð 5.ÁHÁÓÓÃÃRecommendations I.440, I.441, I.450, I.451 and I.452ÄÄ Ð À Ð5.1ÁHÁÃÃRecommendation I.440ÄÄ © ISDN user©network interface data link layer © general aspects (see Recommendation Q.920, Volume VI, Fascicle of the Blue Book) 5.2ÁHÁÃÃRecommendation I.441ÄÄ © ISDN user©network interface, data link layer specification (see Recommendation G.921, Volume VI, Fascicle of the Blue Book) 5.3ÁHÁÃÃRecommendation I.450ÄÄ © ISDN user©network interface layer 3 © general aspects (see Recommendation Q.930, Volume VI, Fascicle  of the Blue Book) 5.4ÁHÁÃÃRecommendation I.451ÄÄ © ISDN user©network interface layer 3 specification for basic call control (see Recommendation Q.931, Volume VI, Fascicle of the Blue Book) 5.5ÁHÁÃÃRecommendation I.452ÄÄ © ISDN user©network interface layer 3 specification © generic procedures for the control of the ISDN supplementary services (see Recommendation Q.932, Volume VI Fascicle of the Blue Book).