When AUTO is selected, the instrument first compares the connected signal with the current status of frame sync and pattern sync. If both are matched with the connected signal, then no further action is taken.
The instrument will also hunt for signal. If the instrument is configured for DS1, and if no DS1 signal is present, then it will change mode to DS3 and test for a signal at the DS3 rate. If the instrument is configured for DS3, and if no DS3 signal is detected, then it will change mode to DS1 and test for a signal at the DS1 rate. The AUTO algorithm does not hunt for subrate payloads.
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.
If the current mode is DS3, then the current DS3 Framing Mode and Line Code configuration are used when testing for Pattern. The default Framing Mode is C-Bit, and the default Line Code is B3ZS. The instrument does not search for Framing Mode when configured for DS3. 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.
