<P> In particular, all telephone modems faster than 300 bit / s use quadrature amplitude modulation (QAM). (QAM uses a two - dimensional constellation). </P> <P> The number of possible pulse amplitudes in analog PAM is theoretically infinite . Digital PAM reduces the number of pulse amplitudes to some power of two . For example, in 4 - level PAM there are 2 2 (\ displaystyle 2 ^ (2)) possible discrete pulse amplitudes; in 8 - level PAM there are 2 3 (\ displaystyle 2 ^ (3)) possible discrete pulse amplitudes; and in 16 - level PAM there are 2 4 (\ displaystyle 2 ^ (4)) possible discrete pulse amplitudes . </P> <P> Some versions of the Ethernet communication standard are an example of PAM usage . In particular, 100BASE - T4 and BroadR - Reach Ethernet standard, use three - level PAM modulation (PAM - 3), 1000BASE - T Gigabit Ethernet uses five - level PAM - 5 modulation and 10GBASE - T 10 Gigabit Ethernet uses a Tomlinson - Harashima Precoded (THP) version of pulse - amplitude modulation with 16 discrete levels (PAM - 16), encoded in a two - dimensional checkerboard pattern known as DSQ128 . </P> <P> The concept is also used for the study of photosynthesis using a specialized instrument that involves a spectrofluorometric measurement of the kinetics of fluorescence rise and decay in the light - harvesting antenna of thylakoid membranes, thus querying various aspects of the state of the photosystems under different environmental conditions . </P>

Which of the following pulse modulation is analog