What is a Digital Service (DS) level and framing specification for digital streams over circuits in the North American transmission hierarchy at 1.544 Mbps?

In the North American transmission hierarchy, a Digital Service (DS) level refers to the specific capacity or rate of digital data that can be transmitted over a circuit. At 1.544 Mbps, this is categorized as DS-1, which is the first level in the hierarchy. DS-1 streams can carry 24 voice channels or equivalent data, and they are framed using a technique called T1 framing, which organizes the data into a structured format for efficient transmission and error detection.