单项选择题
A. signal fail， signal degrade， manual switch
B. signal degrade， signal fail， manual switch
C. protection lockout， manual switch， path AIS
D. forced switch， manual switch， signal degrade
E. protection lockout， manual switch， forced switch
单项选择题 WhatprotocolenablesEthernetoverSONET/SDHencapsulationinteroperabilitybetweentheG-seriesandML-seriesEthernetcards？（）
单项选择题 You are provisioning an E-1 circuit on an ONS 15454 MS-SPRing configuration and XC-VXL-10G card. Each VC-12 connection must also terminate via the VC-3 matrix. How many VC-3 ports remain after this circuit is created， assuming no other circuits？（）
单项选择题 Whatisthedifferencebetween1+1and1：1protectionswitching？（）