A+ Certification ™ Practice Questions Modem Signals

Q7.   Which control signal on a serial cable, indicates that the data set is ready?

A.    DTR

B.    DSR

C.    RTS

D.    CTS

Correct Answer: B.        CompTIA A+ Certification Training ...practice questions...Explanation follows:

Explanation:

COM1, COM2 on a computer uses serial cable. The pin assignments are shown below. The computer acts as a DTE(Data Terminal Equipment) and the Modem acts as DCE (Data Communication Equipment).

Signal--Name---------DB9 Pin

RX------Received Data--2

TX------Transmitted Data-3

DTR-----Data Terminal Ready--4

GND---- Ground--5

DSR---- Data Set Ready--6

RTS---- Request to Send--7

CTS---- Clear to send--8

Normally, a DTE device connects to a DCE device with a straight cable. If you want to connect two DTR devices, as you would do to hook up two computers via the serial line to exchange files, the cable itself must have cross connections. Such a cable is called null modem cable.