Which of the following is not a modem?

A.
ISDN

B.
CSU / DSU

C.
Cable

D.
DSL

Explanation:
While a CSU / DSU connect a digital carrier line, such as the T-series or the DDS line to your
network, it does not perform modulation and demodulation.
Incorrect Answers:
A: ISDN, Cable and DSL are all modems that modulate digital data onto an analog carrier for
transmission over the internet and demodulates from the analog carrier to a digital signal at the
receiving end.Reference:David Groth and Toby Skandier, Network+ Study Guide (4th Edition),
Sybex, Alameda CA, 2005, p. 63-69, 293.
C: ISDN, Cable and DSL are all modems that modulate digital data onto an analog carrier for
transmission over the internet and demodulates from the analog carrier to a digital signal at the
receiving end.Reference:David Groth and Toby Skandier, Network+ Study Guide (4th Edition),
Sybex, Alameda CA, 2005, p. 63-69, 293.
D: ISDN, Cable and DSL are all modems that modulate digital data onto an analog carrier for
transmission over the internet and demodulates from the analog carrier to a digital signal at the
receiving end.Reference:David Groth and Toby Skandier, Network+ Study Guide (4th Edition),
Sybex, Alameda CA, 2005, p. 63-69, 293.