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Checking Signal Status This section describes how to use the CTS850 to check signal status. The CTS850 SDH/PDH Test Set continuously monitors the input signal for alarms, errors, and failures and provides indicators for the current signal status as well as indicating the history of the signal status. Viewing Signal Structure The quickest way to view the structure of a signal is to use AUTOSCAN. AUTOSCAN analyzes the input signal and once a signal is found, the CTS850 synchronizes with the signal and displays the structure of the signal. To view signal structure using AUTOSCAN: 1. Connect a signal to the receiver input. 2. If a test is running, stop the test by pressing START/STOP. 3. Press the AUTOSCAN front-panel button. While AUTOSCAN is running, several messages appear in the display. While the CTS850 searches for a signal it displays the message: Please wait, autosetting to received signal. The CTS850 scans all line rates and all receiver input connectors until it finds a valid SDH or PDH signal. When the CTS850 finds a valid signal, the instrument displays the message: Autosetting to received signal. If a signal is not found, a message to that effect is displayed. When the AUTOSCAN finishes, the CTS850 displays the signal structure in graphical form (see Figure 3 22). Use the knob to scroll through the different active channels. CTS850 SDH/PDH Test Set User Manual 3 63 Checking Signal Status Figure 3 22:The AUTOSCAN Dialog Box Showing Signal Structure Viewing the Payload If the received signal uses tributary mapping, then Autoscan can display the different tributaries within the AU. To display the tributary payload, highlight an AU-4 where TU12 or TU3 is shown as the mapping and select the Show Payload choice (see Figure 3 23). 3 64 CTS850 SDH/PDH Test Set User Manual Checking Signal Status Figure 3 23:Viewing Tributary Signal Structure Determining the Payload Pattern and Framing To search for a pattern in the data of the received signal or determine the framing, select Analyze TU. After you select Analyze TU, the CTS850 scans the selected TU in the received signal to see if it there is a pattern within the data and if the signal is framed. If a pattern is found, it is displayed below the payload map on the Pattern line (for example, PRBS 2^23 1). If the CTS850 is unable to find a pattern within the signal, it displays Unknown on the Pattern line. The CTS850 will display the specific framing in use, on the Framing line. To scan every TU in the received signal, sel