There are seventeen command options available on the NCC 2020 diagnostics menu. Table 5-2 lists all of these commands.
Drawings which illustrate the various loopbacks can be found in the manual AS2000, The Basics.
FOREVER is suggested by Verilink.
Establishes a repeater loopback.
The CSU loops data it is about to transmit back to the receive circuitry. Local equipment should see its own signal.
Useful for testing local CSU hardware.
This test is functionally equivalent to placing a T1 loopback plug into the network port of the CSU.
Establishes an equipment loopback.
The local DSX-1 equipment port is looped back directly to the local equipment. Useful for verifying cable connections.
Displays test error counter, increments for each error detected.
Used to monitor a test in progress. When the CSU transmits a test pattern, it expects to receive the same test pattern unaltered, either from a loopback or a compatible test signal source.
Resets test error counter.
Used to reset the test error counter to zero after a test or before a new test.
Ends tests and local loopbacks.
Used to end any running test patterns as well as terminating any loopbacks in the local CSU.
Starts QRSS test.
CSU transmits a Quasi-Random test pattern while monitoring the receive pair for the same signal to be returned.
This test is widely supported by telephone carrier test facilities.
This test pattern is valid for all T1 circuit types.
Starts 3 in 24 test.
CSU transmits a 3-in-24 test pattern while monitoring the receive pair for the same signal to be returned.
3-in-24 guarantees that of any 24 bits sent, at least 3 will be ones, thus strings of twenty one contiguous zeroes are possible.
Because this pattern may have strings of up to 21 zeroes in a row, it may fail on some perfectly good AMI T1 circuits as equipment in the circuit enforces ones density.
Z) reset alarm
T) test time
2) 3 in 24
Clears alarm history for the current 15 minute interval.
Extinguishes red LED alarm conditions on front panel of the NCC 2020 CSU after installation or after resolving a service problem.
Sets the length of time tests and loopbacks will be allowed to run.
ENTER INTERVAL (DEFAULT, x SEC, x MIN, x HR, FOREVER):
Type FOREVER or type a numeric value followed by SEC for seconds, MIN for minutes, HR for hours.
Exits to menu above.
Determines whether CSU will respond to received standard CSU loop-up codes.
Returns to the NCC 2020 Main Menu. Normally this selection should be enabled.
In a telephone carrier central office environment this option might be disabled.
Verilink NCC 2020 User Manual