Inter-exchange signaling
		n Channel associated signaling (CAS) as No.5, R1, R2 n analog and digital connections n Modern ISDN exchanges apply SS7(digital), that is a common channel signaling method (CSS) that is discussed later in its own lecture n CAS is divided into line and register signaling: n Line signaling: n line state between the trunk-links as n answer, clear-forward*, clear-back n Register signaling: n routing information as n B-number, A-category, B-status
			*A-subscriber on-hook message transmitted to B exchange