Black Box ME444A-R3, ME444AE-R3, ME445C-X.21 manual Local Digital Loopback, Remote digital loopback

Page 45

256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)

LOCAL

DTE

REM

DEPRESSED

DATA

 

CLK

XMTR

CLK

DATA RCVR

RCVR

XMTR

REMOTE

DTE

Figure 6-5. Remote digital loopback.

6.6 Local Digital Loopback

Activate the local digital loopback test by pressing the DIG button on the line driver’s front panel. This test involves creating an outbound loopback at the local line driver (see Figure 6-6 on the next page). It works the same way as if the remote operator had initiated a remote digital loopback at the remote site. With this test, the remote operator can check the performance of the remote and local line drivers and the line between them:

1.Press DIG; the local line driver will signal the remote unit and will start local digital loopback. The TEST LED should light on both units. The local line driver’s receive input should be connected to its own transmitter.

2.Perform a Bit Error Rate Test (BERT). Either:

Hook up an external BERT unit in place of the remote DTE; or

Use the remote line driver’s internal BERT. Press the PATT button. The ERR LED should light briefly just to confirm that the LED is working, and then the test will proceed. If errors are detected, the ERR LED will be continuously lit (if the errors are continuous) or will blink (for intermittent errors).

3.If the BERT test indicates a fault, but both line drivers pass their modem self- tests (see Section 6.3), there is a problem somewhere in the communication line between the units.

44

Image 45
Contents Kbps Line Driver FCC and IC RFI Statements Safety Warnings Declaration of Conformity Kbps Line Driver V.35, RS-530, or NOM Statement Trademarks Used in this Manual Contents Flow Control None SpecificationsSpecifications Physical Description IntroductionFunctional Description Line driver block diagramModulation Timing Point-to-point application ApplicationsTail-circuit application Configuration Placement of the Standalone VersionInstalling the Card Version in the RackNest 2/14 Description of the Racknest 2/14’S Power Supply User-configurable options Configuring the Standalone or Card VersionUser-configurable options Layout of the 256-kbps Line Driver circuit board Kbps Line Driver V.35, RS-530, or Installing the Standalone Version in 19-Inch Racks InstallationInstalling a single unit in a 19-inch rack Installing two units in a 19-inch rack Installing a card in the RackNest 2/14 Installing the 256-kbps Line Driver Rackmount Card VersionRackNest 2/14 illustrated Function Installation Kbps Line Driver V.35, RS-530, or Signal ITU-TSS Lead Name Abbrev Circuit Type Rack Norm Nest PIN Pinout of the V.35 standalone’s M/34 connector DB25 DA15 Connecting Data Cables Line Connection Installation Operation Controls and IndicatorsOperation Indicators Operating ProcedureTroubleshooting Bit-Error-Rate Tester BertLoop Tests Bert using loops Local Analog Loopback Modem Self-TestLocal analog loopback Remote Digital Loopback Remote digital loopback Local Digital LoopbackLocal digital loopback Calling Black BoxShipping and Packaging 19-AWG 22-AWG 24-AWG 26-AWG Kbps Miles Appendix Maximum DistancesCopyright 2004. Black Box Corporation. All rights reserved