单项选择题
WhichstatementsistrueaboutForeignExchangeStation(FXS)portsonarouter?()
A.theFXSinterfaceallowsananalogconnectiontobedirectedatthepublicswitchedtelephonenetwork(PSTN’s)centraloffice
B.theFXSinterfaceconnectdirectlytoastandardtelephone,faxmachine,orsililardeviceandsuppliesring,voltage,anddialtone
C.theFXSinterfaceconnectdirectlytoanIPphoneandsuppliesring,voltage,anddialtone
D.theFXSinterfaceconnectdirectlytoISDNvoicechannels