Refer to T1 Fundamentals for an overview of T1 fundamentals.

Displays the selected signal test mode.

DS1 sets the instrument in T1 testing mode. DS3 test mode is for testing T3/DS3 signals.

When AUTO is selected, the instrument first compares the connected signal with the current status of frame sync and pattern sync. If both are synchronized with the connected signal, then no further action is taken.

If the current mode is DS1, then when AUTO is pressed, the instrument first seeks the frame sync (ESF or SF‑D4). If frame sync is found, then the Framing Mode is displayed in the instrument settings summary (at the left side of the data display area). Then the instrument seeks the pattern sync, stepping through all possible patterns. If pattern sync is found, then the Pattern is displayed in the instrument settings summary. The framing mode and pattern are thereby set, and the instrument is ready for use on the connected circuit.

For additional explanation of the use of this key, refer to section AUTO Signal Setup Explanation.