Norstar MICS Services Cartridge (NTBB24GA-93) provides the clocking service necessary for digital networks. Required if using DTI cartridge(s) or ISDN-BRI Interface cartridge(s). One services cartridge supports all clocking required, regardless of the number or mixture of DTIs and/or ISDN-BRI Interface cartridges. Uses Slot 1 of the core ICS and cannot be used if a Copper Expansion Upgrade Cartridge is installed. Compatible with the Modular ICS core only Additional Details ------------------------------ Product description: Norstar MICS Services Cartridge (NTBB24GA-93) provides the clocking service necessary for digital networks. Required if using DTI cartridge(s) or ISDN-BRI Interface cartridge(s). One services cartridge supports all clocking required, regardless of the number or mixture of DTIs and/or ISDN-BRI Interface cartridges. Uses Slot 1 of the core ICS and cannot be used if a Copper Expansion Upgrade Cartridge is installed. Compatible with the Modular ICS core only