Sample Loopback CSU Full T1 BERT Test

Use this test mode to perform a measurement, such as BERT, on a known test pattern being sent from the far end. The far end signal will be generated by looping back the transmitted signal from this test set. You will use this test set to send a code to automatically loop-up either a CSU or NIU at the far end. Since a pattern is being sent on the T1 line, service on the T1 will be affected.
Once you have selected this test mode, you can send the loop-up or loop-down code using the buttons on the Control menu. If you are you are using ESF, configure the appropriate ESF Loop Code on the Setup menu.
The T1 circuit is not available for service when using this test mode. End-to-end loopback tests are normally limited to the CSU since NIU loop codes are normally suppressed at the central office.
 When the far end of a T1 circuit is in a remote location and trouble is suspected, it is possible to place the equipment at the far end into loopback by sending a special code designated for this purpose. If the T1 circuit is leased, then the wireless technician is often limited to looping only the CSU, as NIU loop codes are usually blocked at the central office. The loop code can be sent either in-band or on the ESF datalink channel by the test set to the far end equipment. The first method, in-band, replaces the bits in the T1 traffic channels with the unique loop code. The remote equipment must see this code for 5 seconds before it will respond in order to minimize the potential that patterns in live data will falsify this request. The downside of this technique is that all devices in the transmit path see this code and any may respond. This could lead to a confusing situation if a T1 route consists of multiple hops, each with its own CSU pair. If the far end has a hard loop then the loop code could come back to the near end and inadvertently place that CSU into loopback. The test set does monitor for a pre-existing loop and will notify you when remote loopback is attempted using an in-band loop code.
 Another method is available if the circuit is designed for Extended Super Frame (ESF). This method, ESF datalink, sends the loop code on the ESF data link bits. This method is not prone to false information and, therefore, responds very rapidly. This is the default mode of the test set. For more information, see the section detailing loopback operation.
 To Preform a Loopback CSU Full T1 BERT Test

Step
 		Notes
1
 		Connect the BSTS to the DSX panel
 		Refer to the Measurement Guide
2
 		[Mode]
3
 		[Backhaul]
4
 		[T1 Analyzer]
5
 		Select a test mode.
  1. [Get Started/ Test Mode]
  2. [Loopback CSU/NIU]
  3. [CSU Full T1 BERT]
Use this test mode to perform measurements such as BERT on a T1 circuit by placing the far end CSU or NIU into a loopback state. The T1 circuit is not available for service when using this test mode. End-to-end loopback tests are normally limited to the CSU since NIU loop codes are normally suppressed at the central office.
Select this to perform a BERT test on a full T1 Circuit.
6
 		[Setup]
 		Select this to display a list of setup choices that pertain to this test mode.
7
 		Setup Rx input.
  1. [Rx Input]
  2. [Terminate]
This assumes the test set is connected into a jack that interrupts the T1 circuit.
8
 		Setup line code.
  1. [Line Code]
  2. [B8ZS]
This assumes the circuit is designed for B8ZS.
9
 		Setup framing.
  1. [Framing]
  2. [ESF]
This assumes that the circuit has been designed for ESF.
10
 		Select a pattern.
  1. [Pattern]
  2. Use the up and down buttons to select.
  3. QRSS
  4. [Select]

11
 		Setup Tx clock.
  1. [Tx Clock]
  2. [Internal]
This is the default selection after test set preset and covers the situation when a hard loop is configured at the far end. If a separate test set is used at each end then the test set on one end should have the Tx Clock set to Primary Rx (assuming the incoming signal is connected to this jack.) Another alternative is to use a second T1 circuit connected to the Secondary Rx jack to establish proper timing.
12
 		Setup the Tx LBO.
  1. [Tx LBO]
  2. [0 dB]
This is a typical level found at the customer demarcation point.
13
 		Setup the loop code.
  1. [Loop Code]
  2. [In-band]
Your choice depends on the far end CSU configuration.
14
 		Setup the slip reference.
  1. [Slip Ref]
  2. [None]
Disables the frame slip measurement.
15
 		Setup the second Tx.
  1. [Second Tx]
  2. [AIS]
Use the default condition.
16
 		Setup the display.
  1. [Display]
  2. [Status]
  3. [Pri]
Enables the [Display] options on the buttons on the right. Activates only the Primary Status pane. The inactive channel should be deactivated to cease the display of invalid measurements.
17
 		Setup the alarms.
  1. [Alarms]
  2. [Pri]
This selection causes the Alarm pane to toggle between Primary and Secondary. Use this selection to observe the Primary Results in the Alarm Panel.
18
 		Setup the results display.
  1. [Results]
  2. Use the up and down arrows to select.
  3. Make a selection.
  4. [Select]
Enables a list of results information that can be displayed in the Results pane. Make a selection based on the need of the application.
19
 		Setup the controls and select a pattern.
  1. [Control]
  2. [Pattern]
  3. Use the up and down buttons to select.
  4. QRSS
  5. [Select]

20
 		Select the alarm.
  1. [Alarm/Error]
  2. Use the up and down buttons to select.
  3. Loss of Signal
  4. [Select]

21
 		[Send Loop Up]
 		Sends a loop up command to the far end and reports the loop state on the status line. If a pre-existing loop is detected at the far end then "Pre-existing loop" is displayed on the status line. This is only possible in In-band mode.
22
 		[Send Loop Down]
 		Sends a loop down command to the far end and reports the loop state on the status line.
23
 		Inject an error.
  1. [Inject]
  2. [On]
Causes the error or condition that is currently displayed on the button to occur.