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Black Box RS-232 Instruction

Long-haul modem
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MARCH 2001
ME380A
19.2-kbps RS-232 Long-Haul Modem
(LHM-19.2)
1 9 . 2
L H M -
P A T T
R E M
A N A
D I G
S Q
T E S T
D C D
R D
T D
R T S
P W R
CUSTOMER
Order toll-free in the U.S.: Call 877-877-BBOX (outside U.S. call 724-746-5500)
SUPPORT
FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746
INFORMATION
Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • E-mail: info@blackbox.com

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  • Page 1 Order toll-free in the U.S.: Call 877-877-BBOX (outside U.S. call 724-746-5500) SUPPORT FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746 INFORMATION Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018 Web site: www.blackbox.com • E-mail: info@blackbox.com...
  • Page 2 TRADEMARKS USED IN THIS MANUAL BLACK BOX and the logo are registered trademarks of Black Box Corporation. Any other trademarks mentioned in this manual are acknowledged to be the property of the trademark owners.
  • Page 3 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) EUROPEAN UNION DECLARATION OF CONFORMITY The manufacturer declares that the LHM-19.2 conforms to the following EMC and safety standards: • EN55022 (1994): “Limits and methods of measurement of radio disturbance characteristics of information technology equipment.”...
  • Page 4 NOM STATEMENT NORMAS OFICIALES MEXICANAS (NOM) ELECTRICAL SAFETY STATEMENT INSTRUCCIONES DE SEGURIDAD 1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de que el aparato eléctrico sea operado. 2. Las instrucciones de seguridad y operación deberán ser guardadas para referencia futura.
  • Page 5 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 12. Precaución debe ser tomada de tal manera que la tierra fisica y la polarización del equipo no sea eliminada. 13. Los cables de la fuente de poder deben ser guiados de tal manera que no sean pisados ni pellizcados por objetos colocados sobre o contra ellos, poniendo particular atención a los contactos y receptáculos donde salen del...

  • Page 6: Table Of Contents

    6.1.2 ANA Button: Local Analog Loopback ........30 6.1.3 REM Button: Remote Digital Loopback ....... 31 6.1.4 DIG Button: Local Digital Loopback ........33 6.2 Calling Black Box ................34 6.3 Shipping and Packaging ..............34 Appendix: RS-232 Pinout ................35...

  • Page 7: Specifications

    Electrical safety: CE (EN60950, EN41003) Cable Required — Between ME380A units: 4-wire twisted pair, 19 to 26 AWG; Between ME380A and DTE: EIA/TIA RS-232 cable with DB25 male connector on ME380A end To line: 4-wire telco style (do not connect to PSTN);...
  • Page 8 CHAPTER 1: Specifications Adaptive Equalization — Synchronization Delay — Startup: Up to 8 seconds; Resync: Up to 5 seconds Line Type — 4-wire, at least voice-grade Maximum Transmission Distance — Unloaded lines: Up to 37.2 miles (60 km)—see Table 1-1; Conditioned lines: Up to 62 miles (100 km), depending on line quality Table 1-1.
  • Page 9 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) Continuous line-quality testing (results indicated with Diagnostics — SQ LED and optionally with SQD signal); V.52 compliant bit error rate testing with pseudo-random bit patterns (results indicated with SQ LED and optionally with SQD signal);...

  • Page 10: Introduction

    For diagnostics, the LHM-19.2 performs continuous line tests. It indicates line quality with the SQ LED and (optionally) the RS-232 SQD signal: The LED stays ON and the signal stays high if quality is good, but if the bit error rate ever rises above...
  • Page 11 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) DTE (PC, server, etc.) DTE (PC, server, etc.) 4-wire line LHM-19.2 LHM-19.2 Figure 2-1. Two LHM-19.2s in a direct point-to-point application. LHM-19.2 LHM-19.2 Digital Service Network DTE (PC, DTE (PC, server, server, etc.) etc.) 4-wire...

  • Page 12: Functions

    • INT (internal clock from the LHM-19.2’s own crystal oscillator) • EXT(external clock from the attached DTE device, through RS-232 Pin 24) • LOOP (receive clock recovered from receive signal and looped back) In the vast majority of cases, one modem should be strapped to INT or EXT clock,...
  • Page 13 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) Async-to-Sync Converter If you configure the LHM-19.2 to accept asynchronous data and attach it to a DTE that sends async data, the LHM-19.2 uses its internal V.14-compliant async-to-sync converter to add clock timing to the data for transmission to the remote unit.
  • Page 14 CHAPTER 2: Introduction Receiver The LHM-19.2’s receiver is comprised of several interlinked circuits, as Figure 2-3 shows: • The receive filter removes out-of-band signals and prevents signal spectrum aliasing during analog-to-digital conversion. • The receive signal then passes into a fixed pre-emphasized line equalizer. •...

  • Page 15: Configuration

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 3. Configuration To set the LHM-19.2’s internal jumpers and switches, take these steps, making sure that the modem is unplugged: 1. Loosen the two screws at the lower corners of the LHM-19.2’s rear panel. 2. Slide the inside of the LHM-19.2 out of its housing, as if you were sliding a drawer open.
  • Page 16 CHAPTER 3: Configuration Figure 3-1. The LHM-19.2’s circuit board.
  • Page 17 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) Table 3-2. The LHM-19.2’s configuration settings. Number in Function Possible settings Factory- Figure 3-1 default and identity setting Select data rate. 0 = 1.2 kbps Data-rate dial 1 = 2.4 kbps 2 = 4.8 kbps 3 = 9.6 kbps...
  • Page 18 CHAPTER 3: Configuration Table 3-2 (continued). The LHM-19.2’s configuration settings. Number in Function Possible settings Factory- Figure 3-1 default and identity setting 600 = 600 Ω 600 Ω Select transmit-line XMT IMP impedance. LOW = Min. impedance* 600 = 600 Ω 600 Ω...

  • Page 19: Installation

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 4. Installation The 19.2-kbps RS-232 Long-Haul Modem comes with a 5-ft. (1.5-m) power cord and this manual. It’s designed to be placed either on a flat surface or in a rack. Things to keep in mind about where you place it: •...

  • Page 20: Rackmounting A Single Lhm-19.2

    CHAPTER 4: Installation 4.1.1 R LHM-19.2 ACKMOUNTING A INGLE The single-chassis rackmount kit RM516 includes one short bracket and one long bracket. You’ll screw the brackets against the side walls of the LHM-19.2’s case, as shown in Figure 4-1. Figure 4-1. Preparing a single LHM-19.2 for mounting in a 19" rack. Take these steps to install the LHM-19.2 in a 19"...

  • Page 21: Rackmounting Two Lhm-19.2S Side By Side

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 4.1.2 R LHM-19.2 ACKMOUNTING IDE BY The dual-chassis rackmount kit RM523 includes two rails for attaching the LHM-19.2s together, two short brackets, and various other hardware. Referring to Figures 4-2 and 4-3 on the next page, take these steps to install two LHM-19.2s side by side in a 19"...
  • Page 22 CHAPTER 4: Installation Figure 4-2. Preparing each LHM-19.2 for dual rackmounting. Figure 4-3. Fastening the two LHM-19.2s together.

  • Page 23: Connecting Data Cables

    “DTE” because for most applications you will plug a DTE into it. The type of cable you’ll run from this port to your local RS-232 device will vary depending on what type of device it is. Here are some typical options: •...
  • Page 24 CHAPTER 4: Installation Attach each of the twisted-pair wires to one of the LHM-19.2’s terminals this way: 1. Insert the end of a screwdriver into the square hole above the terminal. 2. Lever the screwdriver handle upwards to put pressure on the element at the bottom of the square hole.

  • Page 25: Connecting Power

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 4.3 Connecting Power The LHM-19.2 gets its power through an included 5-ft. (1.5-m) power cord. After you read the Caution notices below, plug one end of this cord into the IEC 320 male inlet on the LHM-19.2’s rear panel, then plug the other end into a working 115-VAC wall outlet.

  • Page 26: Operation

    5. Operation 5.1 Power-Up Make sure that the 19.2-kbps RS-232 Long-Haul Modem is fully configured and installed (see Chapters 3 and 4). Then, if you haven’t already done so, plug the LHM-19.2’s power cord into a working AC outlet. The LHM-19.2 should begin operating immediately.
  • Page 27 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) Table 5-1. The front-panel pushbuttons. BUTTON LABEL FUNCTION Pressing this Local Digital Loopback button causes the local LHM-19.2 to loop received data and clock to its transmitter. Data Set Ready goes low. This is equivalent to initiating Remote Digital Loopback (V.54 Loop 2) at the remote LHM-19.2.

  • Page 28: Power-Down

    CHAPTER 5: Operation 5.3 Power-Down To turn the LHM-19.2 off, unplug its power cord. 5.4 Reconfiguration If at some point you need to reconfigure the LHM-19.2 to operate differently— with a new data rate or new clock source, for example—you can change the settings of its configuration controls.

  • Page 29: Troubleshooting

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 6. Troubleshooting 6.1 Tests and Diagnostics This section describes how the LHM-19.2’s diagnostic tests work and explains how to isolate faults. The LHM-19.2 has ITU V.54 compliant diagnostic capabilities for performing local analog loopback and local and remote digital loopback. All three of these loopbacks can be controlled with the LHM-19.2’s front-panel pushbuttons.
  • Page 30 CHAPTER 6: Troubleshooting PATT PRESSED PRESSED XMTR PATTERN GENERATOR PATTERN RCVR TESTER LHM-19.2 Figure 6-1. Single-modem BERT during local analog loopback. PATT PRESSED (Disconnects PATT External BERT) PRESSED PATTERN PATTERN GENERATOR TESTER PATTERN PATTERN TESTER GENERATOR LHM-19.2 LHM-19.2 Figure 6-2. Dual-modem BERT.

  • Page 31: Ana Button: Local Analog Loopback

    19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) 6.1.2 ANA B UTTON OCAL NALOG OOPBACK This test checks the performance of the local LHM-19.2, the device attached to it, and the cabling between the LHM-19.2 and the device. Perform the test separately at the local and remote sites.

  • Page 32: Rem Button: Remote Digital Loopback

    CHAPTER 6: Troubleshooting PRESSED DATA XMTR DATA TERMINAL LINE DATA RCVR LHM-19.2 Figure 6-3. Local analog loopback. 6.1.3 REM B UTTON EMOTE IGITAL OOPBACK This test checks the performance of both the local and remote LHM-19.2s, as well as the twisted-pair cabling between them. 1.
  • Page 33 LHM-19.2s. Try connecting the two modems with a known-good twisted-pair line. If this doesn’t help, the line circuits in one or both modems are probably faulty; call Black Box Technical Support. 4. Press the REM pushbutton again, or lower the signal on Pin 21, to end this loopback.

  • Page 34: Dig Button: Local Digital Loopback

    If this doesn’t help, the line circuits in one or both modems are probably faulty; call Black Box Technical Support. 4. Press the DIG pushbutton again to end this loopback. PRESSED...

  • Page 35: Calling Black Box

    6.2 Calling Black Box If you determine that your LHM-19.2 is malfunctioning, do not attempt to alter or repair the unit. It contains no user-serviceable parts. Contact Black Box Technical Support at 724-746-5500. Before you do, make a record of the history of the problem. We will be able to...

  • Page 36: Appendix: Rs-232 Pinout

    APPENDIX: RS-232 Pinout Appendix: RS-232 Pinout EIA/TIA DB25 Signal or Description V.24 RS-232 Pin Voltage Circ. Circuit Shield [SHD] Chassis ground. May be connected to Signal Ground or isolated from it—see Chapter 3. Signal Ground [SGND] Common signal ground and DC power-supply ground.
  • Page 37 19.2-KBPS RS-232 LONG-HAUL MODEM (LHM-19.2) EIA/TIA DB25 Signal or Description V.24 RS-232 Pin Voltage Circ. Circuit Receive Line Signal The modem keeps this signal Detector [RLSD], high to the attached device a.k.a. Data Carrier except when the receive signal Detect [DCD] from the other modem is lost or when DSR on Pin 6 goes low.
  • Page 38 © Copyright 2001. Black Box Corporation. All rights reserved. 1000 Park Drive • Lawrence, PA 15055-1018 • 724-746-5500 • Fax 724-746-0746...

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