As opposed to other DSL technologies, SHDSL employs trellis-coded pulse-amplitude modulation (TC-PAM).
As a baseband transmission scheme, TC-PAM operates at frequencies that include those used by the analog voice plain old telephone service (POTS).
The two pair feature may alternatively be used for increased reach applications by keeping the data rate low.
With the 32-TC-PAM modulation scheme described in Annexes F and G, symmetric data rates of up to 5,696 kbit/s are permitted on one pair in the optional extended SHDSL mode.
The updated G.991.2 features: SHDSL supersedes the older HDSL symmetric DSL technology defined in ITU-T G.991.1.