Study on subscriber line circuits applicable for analogue telephone and ISDN interfaces

The mixed installation of analog interfaces and ISDN (integrated services digital network) interfaces in an ISDN switching system is important for a smooth transition to full-scale ISDN. The subscriber line interface circuit which can accommodate analog and ISDN interfaces is discussed. The following issues are considered: (1) accommodation of analog and ISDN interfaces in the ULIC (unified subscriber line interface circuit); (2) composition of the ULIC; (3) construction and functionality of the analog/ISDN signal conversion adapter; and (4) the impact of the ULIC on the switching system