The Cisco ONS 15327 is designed for total front panel access so there are no connectors on the backplane. This is made possible through the use of Mechanical Interface Cards (MICs) in Slots 7 and 8. The MICs are (mostly) passive cards that provide interfaces for power, timing, and external alarms, as well as the physical interfaces for DS3s and DS1s. You should think of these cards as connections only, similar to the backplane connectors on the 15454. The MICs do not contain any DS3 or DS1 circuitry and they do not provide protection-switching operations. All DS-n functions are managed from the XTC cards, including the DS-n switching.There are two types of MIC cards, A and B. Both cards have DS1 amphenol cable interfaces, compression-type power connectors, and RJ-45 alarm and timing interfaces. MIC B has the three receive DS3 interfaces and is keyed for Slot 7. Only one MIC is necessary to operate the 15327, but simplex operation means non-redundant power and timing and no DS3 provisioning.