Adtran Atlas 550 Quad ISDN BRI U Module 1200315L1 Routers and YY741 stacking modules are

and YY741 stacking modules are supported by the switch

35 Module 1200346L2 Description:

Inter-Tel 8500 Series Grey Handsets Description:

The Inter-Tel Axxess 550

Adtran Atlas 550 Quad ISDN BRI U Module 1200315L1 Routers and YY741 stacking modules areAdtran Atlas 550 Quad ISDN BRI U Module 1200315L1 Description: The Adtran 1200315L1 provides 4 ISDN U Interfaces for User Termination applications. The Quad ISDN BRI U module supports AT&T 5ESS, Nortel DMS 100, and National ISDN 1. The Adtran 1200315L1 is compatible with Atlas 550 gateways. Adtran 1200315L1 Features: Provides four BRI S T interfaces Supports: AT&T 5ESS Nortel DMS 100 National ISDN 1 Can only be used in a user interface module slot.