U-NT and U-LT loops can be used in combination to provide D-packet service for a point-of-sale terminal adapter (POSTA) or other D-packet device. D-packet service is a 16 kbps data transmission service that uses the D-channel of an ISDN line. To deliver D-packet service, a network connection (U-NT) is programmed to work with a terminal connection (U-LT). The loops must be on the same physical card. For example, if the network connection is a loop found on the BRI Card in Slot 1, the terminal connection must be a loop found on the same card. S reference point The S reference point connection provides either a point-topoint or point-to-multipoint digital connection between Norstar and ISDN terminal equipment (TE) that uses an S interface. S loops support up to seven ISDN DNs, which identify TE to the ICS.