# OTN – Lesson 10 – Video 2M – The OTUk/ODUk_A_Sk and ODUk_TT_Sk Atomic Functions

This blog post includes a video that begins our discussion of the Sink (or Receive) Direction Atomic Function/Circuitry for the ODU-Layer/Multiplexed Applications.

In particular, this video reviews the following Atomic Functions

- OTUk/ODUk_A_Sk Function
- ODUk_TT_Sk Function

* NOTE:* Even though we did review these functions back in the Non-Multiplexed portion of Lesson 10 Training; I wanted to review the Consequent Equations for these functions (once again), because these equations do impact the signals that the ODUkP/ODUj-21_A_Sk function (downstream) will “see”.

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