Black Box Network Router ME444A 530 R3 User Manual

MARCH 2004  
ME444A-R3  
ME444AE-R3  
ME444A-530-R3  
ME444AE-530-R3  
ME445C-35  
ME445C-530  
ME445C-X.21  
256-kbps Line Driver  
(V.35, RS-530, or X.21)  
CUSTOMER  
SUPPORT  
INFORMATION  
Order toll-free in the U.S.: Call 877-877-BBOX (outside U.S. call 724-746-5500)  
FREE technical support 24 hours a day, 7 days a week: Call 724-746-5500 or fax 724-746-0746  
Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Safety Warnings  
Always observe standard safety precautions during installation,  
operation, and maintenance of this product. Only qualified and  
authorized service personnel should adjust, maintain, or repair this  
instrument. Do not attempt to adjust, maintain, or repair the equipment.  
Telecommunication Safety  
The safety status of each of the ports on the line driver appears below:  
Ports  
Safety Status  
V.24, V.35, V.36, X.21, RS-530  
LAN  
SELV  
Circuit operating with  
Safety Extra-Low Voltage  
G.703, Line  
TNV-1 Circuit whose normal  
operating voltage is  
within the limits of SELV,  
on which overvoltages  
from telecommuni-  
cations networks are  
possible.  
FCC Part 15 User Information  
This equipment has been tested and found to comply with the limits of a  
Class A digital device, pursuant to Part 15 of the FCC rules. These limits  
are designed to provide reasonable protection against harmful  
interference when the equipment is operated in a commercial  
environment. This equipment generates, uses, and can radiate radio  
frequency energy, and, if not installed and used in accordance with the  
instruction manual, may cause harmful interference to the radio  
communications. Operation of this equipment in a residential area is  
likely to cause harmful interference in which case the user will be  
required to correct the interference at his own expense.  
Warning per EN 55022  
This is a Class A product. In a domestic environment, this product may  
cause interference, in which case the user may be required to take  
adequate measures.  
2
 
Declaration of Conformity/Supplementary Information  
Declaration of Conformity  
The line driver conforms to the following standard(s) or other normative  
document(s);  
EMC:  
EN 55022 (1994)  
EN 50082-1 (1992)  
EN 60950 (1992/3)  
Limits and methods of measure-  
ment of radio disturbance  
characteristics of information  
technology equipment.  
Electromagnetic compatibility—  
Generic immunity standards for  
residential, commercial, and light  
industry.  
Safety:  
Safety of information technology  
equipment, including electrical  
business equipment.  
Supplementary Information  
This product complies with the requirements of the EMC Directive  
89/336/EEC and the Low Voltage Directive 73/23/EEC. The product was  
tested in a typical configuration by the manufacturer.  
3
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
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.  
3. Todas las advertencias en el aparato eléctrico y en sus instrucciones de  
operación deben ser respetadas.  
4. Todas las instrucciones de operación y uso deben ser seguidas.  
5. El aparato eléctrico no deberá ser usado cerca del agua—por ejemplo, cerca  
de la tina de baño, lavabo, sótano mojado o cerca de una alberca, etc..  
6. El aparato eléctrico debe ser usado únicamente con carritos o pedestales que  
sean recomendados por el fabricante.  
7. El aparato eléctrico debe ser montado a la pared o al techo sólo como sea  
recomendado por el fabricante.  
8. Servicio—El usuario no debe intentar dar servicio al equipo eléctrico más allá  
a lo descrito en las instrucciones de operación. Todo otro servicio deberá ser  
referido a personal de servicio calificado.  
9. El aparato eléctrico debe ser situado de tal manera que su posición no  
interfiera su uso. La colocación del aparato eléctrico sobre una cama, sofá,  
alfombra o superficie similar puede bloquea la ventilación, no se debe colocar  
en libreros o gabinetes que impidan el flujo de aire por los orificios de  
ventilación.  
10. El equipo eléctrico deber ser situado fuera del alcance de fuentes de calor  
como radiadores, registros de calor, estufas u otros aparatos (incluyendo  
amplificadores) que producen calor.  
11. El aparato eléctrico deberá ser connectado a una fuente de poder sólo del  
tipo descrito en el instructivo de operación, o como se indique en el aparato.  
4
 
NOM STATEMENT  
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  
aparato.  
14. El equipo eléctrico debe ser limpiado únicamente de acuerdo a las  
recomendaciones del fabricante.  
15. En caso de existir, una antena externa deberá ser localizada lejos de las lineas  
de energia.  
16. El cable de corriente deberá ser desconectado del cuando el equipo no sea  
usado por un largo periodo de tiempo.  
17. Cuidado debe ser tomado de tal manera que objectos liquidos no sean  
derramados sobre la cubierta u orificios de ventilación.  
18. Servicio por personal calificado deberá ser provisto cuando:  
A: El cable de poder o el contacto ha sido dañado; u  
B: Objectos han caído o líquido ha sido derramado dentro del aparato; o  
C: El aparato ha sido expuesto a la lluvia; o  
D: El aparato parece no operar normalmente o muestra un cambio en su  
desempeño; o  
E: El aparato ha sido tirado o su cubierta ha sido dañada.  
5
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
TRADEMARKS USED IN THIS MANUAL  
AS/400 and IBM are registered trademarks of International Business  
Machines Corporation.  
Any other trademarks mentioned in this manual are acknowledged to be the property of the  
trademark owners.  
6
 
CONTENTS  
Contents  
Chapter  
Page  
1. Specifications ............................................................................................. 8  
2. Introduction ...............................................................................................10  
2.1 Physical Description ............................................................................10  
2.2 Functional Description ..................................................................... 11  
2.2.1 Encoder Modulator ................................................................. 11  
2.2.2 Modulation Timing ................................................................ 12  
2.2.3 Signal Levels ........................................................................... 12  
2.2.4 Receiver .................................................................................. 12  
2.2.5 V.54 Diagnostics ..................................................................... 13  
2.2.6 Test-Pattern Generator and Receiver ................................... 13  
2.3 Applications ........................................................................................ 13  
3. Configuration...............................................................................................15  
3.1 Placement of the Standalone Version .................................................15  
3.2 Installing the Card Version in the RackNest 2/14..............................15  
3.3 Configuring the Standalone or Card Version.....................................17  
4. Installation....................................................................................................21  
4.1 Installing the Standalone Version in 19" Racks ..................................21  
4.1.1 Overview .....................................................................................21  
4.1.2 Installing a Single Unit in a 19-Inch Rack................................21  
4.1.3 Installing Two Standalone Units in a 19-Inch Rack.................22  
4.2 Installing the 256-kbps Rackmount Card Version ..............................24  
4.3 Connecting Data Cables.......................................................................33  
4.3.1 Power Connection......................................................................33  
4.3.2 LINE Connection.......................................................................34  
4.3.3 DTE Connection........................................................................34  
5. Operation ...................................................................................................36  
5.1 Controls and Indicators .................................................................... 36  
5.2 Operating Procedure ........................................................................ 38  
6. Troubleshooting ........................................................................................39  
6.1 Loop Tests ...........................................................................................39  
6.2 Bit-Error-Rate Tester (BERT) ..............................................................39  
6.3 The Modem Self-Test ........................................................................ 41  
6.4 Local Analog Loopback ......................................................................41  
6.5 Remote Digital Loopback ...................................................................43  
6.6 Local Digital Loopback ......................................................................44  
6.7 Calling Black Box .............................................................................. 45  
6.8 Shipping and Packaging .................................................................... 46  
Appendix: Maximum Distances ...................................................................... 47  
7
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
1. Specifications  
Compliance: FCC Class A, IC Class/classe A  
Protocol: Synchronous or asynchronous  
Clock Source: Internal, external (from attached device), or receive clock derived  
from the receive signal  
Flow Control: None  
Operation: 4-wire, full- or half-duplex, point-to-point or multipoint  
Data Rate: Sync: 19.2, 32, 48, 56, 64, 72, 96, 112, 128, 144, 192, or 256 kbps  
(user-selectable); Async: 19.2, 28.8, 38.4, 57.6, or 115.2 kbps (user-selectable)  
Maximum Distance: See the tables in the Appendix  
User Controls: (4) Front-mounted buttons: (1) DIG, (1) ANA, (1) REM, (1) PATT;  
(1) Internal data-rate screwdial; (14) Internal jumpers and (1) internal 3-position  
DIP switch for timing, testing, signal levels/impedances, and other features  
Diagnostics: V.54-compliant loopback tests; V.52-compliant BERT  
Standards: Loopback tests: ITU-TSS V.54; BERT: ITU-TSS V.52  
Leads/Signals Supported: See Tables 4-2 through 4-5  
MTBF: 75,500 hours  
Interfaces: Line side: Proprietary; Device side: ITU-TSS V.35  
Connectors: ME444A-R3, ME444AE-R3: (1) 34-pin M-block female, (1) 5-position  
terminal block;  
ME444A-530-R3, ME444AE-530-R3, ME445C-530, ME445C-35,  
ME445C-X21: (1) DB25 female, (1) 5-position terminal block  
Indicators: (7) Front-mounted LEDs: PWR (power), RTS, TD, RD, DCD, TEST,  
ERR (error)  
Temperature Tolerance: 32 to 122°F (0 to 50°C)  
Humidity Tolerance: Up to 90% noncondensing  
8
 
CHAPTER 1: Specifications  
Maximum Altitude: 8000 ft. (2438.4 m)  
Enclosure: High-impact plastic  
Power: ME444A-R3: Directly from outlet through detachable 5-ft. (1.5-m) power  
cord (included); Optimal input: 115 VAC, 60 Hz; Input ranges: 103.5 to  
126.5 VAC, 47 to 63 Hz; Consumption: 5 watts;  
ME444AE-R3: Directly from outlet through detachable 5-ft. (1.5-m) power cord;  
Optimal input: 230 VAC, 60 Hz; Input ranges: 207 to 253 VAC, 47 to 63 Hz;  
Consumption: 5 watts;  
ME445C: From the RackNest 2/14; Consumption: 5 watts  
Size: ME444A/E-R3: 1.8"H x 7.6"W x 9.6"D (4.6 x 19.3 x 24.4 cm), but the buttons  
protrude up to 0.3" (0.8 cm) from the front panel and the connectors protrude  
up to 0.8" (2 cm) from the rear panel;  
ME445C: 6.2"H x 0.9"W x 9"D (15.7 x 2.3 x 22.9 cm)  
Weight: ME444A/E-R3: 3.1 lb. (1.4 kg); ME445C: 0.8 lb. (0.4 kg)  
9
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
2. Introduction  
The 256-kbps Line Driver is a short-range modem for synchronous or  
asynchronous transmission—full- or half-duplex—over unconditioned lines. With a  
range of up to 11.8 miles (19 km), the line driver operates at user-selectable  
synchronous data rates from 19.2 to 256 kbps or asynchronous data rates from  
19.2 to 115.2 kbps. The line driver is available in standalone V.35 or RS-530  
(ME444A/E-R3) or rackmount card V.35, RS-530, or X.21 (ME445C) versions.  
The line driver uses conditional differential diphase modulation (EUROCOM Std.  
D1) to provide immunity from background noise, eliminate normal line distortion,  
and enable efficient transmission and reception of serial data over twisted-pair  
cable. The modem is coupled to the line through isolation transformers which, in  
conjunction with protective circuitry, safeguard against AC or DC overvoltages.  
With this protective circuitry, the line driver can operate even when DC is  
connected to the line.  
Transmit timing is provided internally, derived externally from the PC or terminal,  
or regenerated from the receive signal. Receive timing is always regenerated from  
the receive signal.  
The line driver features V.54 diagnostic capabilities for local analog loopback and  
local and remote digital loopback testing. In the digital loopback mode, the  
operator at either end of the line may test both modems and the line. The  
loopback is controlled either by pressing front-panel buttons or by manipulating  
signals on the V.35, RS-530, or X.21 (DTE) interface.  
The line driver incorporates a built-in Bit Error Rate Tester (BERT). The internal  
BERT enables complete testing of both modems and the line without external test  
equipment. Pressing the line driver’s front-panel PATT button causes the unit to  
generate a pseudo-random test pattern (511-bit, according to ITU-TSS V.52) for  
testing end-to-end connectivity. The ERR LED flashes when a bit error occurs.  
2.1 Physical Description  
The line driver stands alone as a desktop unit, or can be mounted in a 19-inch rack  
with optional brackets (see Section 4.1). Also available is a rackmount card version  
that installs in the RackNest 2/14 (see Section 4.2). For descriptions of the line  
driver’s controls and indicators, see Section 5.1.  
10  
 
CHAPTER 2: Introduction  
2.2 Functional Description  
This section describes the operation of the line driver’s circuit blocks, primarily the  
circuits required for correctly configuring the modem (see Figure 2-1 below).  
Figure 2-1. Line driver block diagram.  
2.2.1 ENCODER MODULATOR  
The encoder modulator receives data from the DTE, then modulates the data  
using the “conditional diphase modulation” technique. You can configure the  
encoder to operate in one of three modes:  
• 4-wire full-duplex (point-to-point)  
• 4-wire half-duplex (point-to-point)  
• 4-wire multipoint  
The appropriate mode is determined by the setting of two jumpers: CARRIER (J2)  
and RTS-CTS DLY (J4). For multipoint applications, two additional jumpers must  
be set: XMT IMP (J13) and RCV IMP (J10). See Section 3.3 for a more detailed  
explanation of the correct jumper settings.  
11  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
NOTE  
In multipoint applications, do not use the 0-msec option for the  
RTS–CTS delay.  
2.2.2 MODULATION TIMING  
This circuit supplies the transmit clock to the encoder. Three clock sources are  
available on the XMT CLK jumper (J3):  
• INT—Internal clock. From the modem’s internal crystal oscillator.  
• EXT—External clock. From DTE.  
• RCV—Receive clock. Recovered from the receive signal.  
There is also an ASY (asynchronous) setting, but this has no function and should  
not be selected.  
2.2.3 SIGNAL LEVELS  
Two options are available for the transmit and receive signal levels: 0 and -6 dBm.  
You can control the transmit level with the XMT LVL jumper. You can control the  
receive level with the RCV LVL jumper.  
2.2.4 RECEIVER  
The receiver comprises several circuits, as shown in the block diagram (see  
Figure 2-1):  
• The RECEIVE FILTER, which removes all the out-band frequencies.  
• The EQUALIZER, which comprises several equalizers activated according to  
data rate.  
• The digital Automatic Gain Control (AGC), which automatically compensates  
for the attenuation of the line.  
12  
 
CHAPTER 2: Introduction  
2.2.5 V.54 DIAGNOSTICS  
V.54 loops are activated manually with the front-panel buttons, or through the  
DTE interface. The buttons and the DTE interface can be enabled or disabled  
separately by jumpers J7 and J8 (shown in Figure 3-1 and described in Table 3-1).  
When you use the line driver as a tail-end to a digital network, the V.54 DLY  
jumper in the modems located close to the network should be set to ON to prevent  
multiple loopbacks. The delay switch is used to prevent the last modem from  
receiving the complete V.54 data sequence and, in turn, being induced into a loop.  
2.2.6 TEST-PATTERN GENERATOR AND RECEIVER  
This feature allows for easy and quick testing of the local modem as well as the  
communication link. When the PATT button on the front panel is pressed, the  
circuit sends and checks a standard 511-bit pseudo-random pattern. If the modem  
encounters errors, the ERR LED remains ON or blinks.  
The test can be carried out in local analog loopback, in remote digital loopback, or  
in normal point-to-point operation opposite a remote line driver modem. Press the  
PATT pushbutton on the remote unit or connect a Bit Error Rate Tester that uses  
the standard 511-bit pattern.  
2.3 Applications  
The diagrams on this page and the following pages illustrate the line driver  
operating in various applications.  
4-wire  
Up to 11.8 mi. (19 km)  
256-kbps  
256-kbps  
Line Driver  
Line Driver  
19.2 to  
256 kbps  
AS/400®  
AS/400  
Figure 2-2. Point-to-point application.  
13  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
4-wire  
twisted pair  
DDS  
(56 kbps)  
External  
clock  
Receive  
clock  
CSU/DSU  
256-kbps  
Line Driver  
CSU/DSU  
256-kbps  
Line Driver  
Sync host  
Sync host  
Tail circuit  
Figure 2-3. Tail-circuit application.  
V.35 interface  
V.35 interface  
4-wire  
twisted pair  
(64 kbps)  
V.35  
cable  
V.35  
cable  
256-kbps  
Line Driver  
V.35 interface  
IBM 3274  
controller  
IBM® S/3X  
mainframe  
V.35  
cable  
256-kbps  
Line Driver  
IBM 3274  
controller  
V.35 interface  
V.35  
cable  
256-kbps  
Line Driver  
IBM 3274  
controller  
Figure 2-4. Multipoint application.  
14  
 
CHAPTER 3: Configuration  
3. Configuration  
This chapter explains how to configure your standalone or rackmount card line  
driver. After you configure it, see Chapter 4 for how to install it, Chapter 5 for how  
to operate it, and Chapter 6 for how to test the system.  
3.1 Placement of the Standalone Version  
Place the 256-kbps Line Driver standalone model within 5 ft. (1.5 m) of a  
grounded, easily accessible AC outlet. The outlet should be capable of providing  
either 115 VAC (for the ME444A-R3 model) or 230 VAC (for the ME444AE-R3  
model).  
The line driver is designed to be placed on a tabletop or bench, and is shipped  
completely assembled. Allow at least 36" (91.4 cm) of frontal clearance for  
operation and access for maintenance. You also need at least 4" (10.2 cm) of  
clearance at the rear of the unit for signal lines and interface cables.  
3.2 Installing the Card Version in the RackNest 2/14  
The RackNest 2/14 is a special 19" rack component designed to host a number of  
our short-haul modems and line drivers. It consists of a rack chassis (with one or  
two power supplies) into which you can plug as many as 14 modem or driver cards.  
The nest’s rear panel consists of fourteen five-screw terminal blocks (“TB1”) and  
fourteen connectors (“J1”). Each terminal block (“TB1”) provides four screws for  
connecting nest-to-nest G.703 transmit and receive lines—the transmit pair can be  
connected to the terminals marked XMT, and the receive pair can be connected to  
the terminals marked RCV—plus a fifth screw for ground connection.  
Each interface connector (“J1”) is a DB25 female. The pinning of this connector  
depends on the type of card installed in the corresponding slot, because the cards  
will present and expect different signals on different pins. For the V.35 model of  
the line driver card (ME445C-35), the pinning is a special V.35-on-DB25 variant;  
for the RS-530 and X.21 models, the pinning is RS-530. Refer to Tables 4-2 through  
4-5 (Chapter 4) for the pinouts of this connector, and for the pinning of the  
adapters or adapter cables that will be necessary to attach a V.35 or X.21 DTE to  
this connector.  
15  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
DESCRIPTION OF THE RACKNEST 2/14’S POWER SUPPLY  
The 115-VAC RackNest 2/14 (our product code RM110A) uses the PS1000A power  
supply, which accepts 115-VAC input power. The 230-VAC RackNest 2/14 uses  
power supply PS1000AE, which accepts 230-VAC input power. Each of these power  
supplies consists of a power-line transformer and a fuse. The 115-VAC nest can also  
be ordered with dual power supplies (our product code RM110A-2PS); either of  
these power supplies can be hot-swapped if it fails.  
All power-regulating circuitry for the RackNest 2/14 is located on the card  
modems themselves. Each card has two fuses which protect the entire system  
against power failure due to a short circuit in one card. Primary power needed is  
115 or 230 VAC 10%, 47 to 63 Hz, at 24 VA maximum.  
AC power should be supplied to the RackNest 2/14 through a standard power  
cable run between the AC mains socket on the rear of the nest’s power-supply  
module—an IEC 320 male power inlet which contains an integral fuse—and a  
standard, grounded, easily accessible AC outlet. (If your nest is an RM110A, you  
can use the power cord supplied with it; if your nest is an RM110AE, use a power  
cord appropriate for your site’s mains outlets.)  
The nest begins operating and supplying power to the installed cards as soon as it  
is plugged into a mains outlet, and will continue operating until it is unplugged.  
WARNING!  
This unit should always be grounded through the protective earth lead  
of the power cable. Before AC power is connected to this unit, the mains  
plug should only be inserted into a socket outlet provided with  
protective earth contact. The protective action must not be negated by  
use of an extension cord without a grounding conductor.  
Whenever it is likely that the unit’s fuse (located in a bayonet-type fuse  
holder on the unit’s rear panel) has been blown or damaged, make the  
unit inoperative and secure it against unintended operation until the  
fuse can be replaced. Make sure that only fuses of the required rating,  
as marked on the rear panel, are used for replacement. Do not use  
repaired fuses or short-circuit the fuse holder. Always disconnect the  
mains cable before removing or replacing the fuse.  
Interrupting the grounding conductor, inside or outside the unit, or  
disconnecting the protective earth contact, can make this unit  
dangerous!  
16  
 
CHAPTER 3: Configuration  
3.3 Configuring the Standalone or Card Version  
Before attaching anything to the 256-kbps Line Driver standalone or rackmount  
card version, determine which data rate you’re going to use, what the system’s  
clock source should be, and how you want to set all of the other user-configurable  
options on the line driver. (Refer to Table 3-1 on the next two pages for a list of all  
of these options; the SWn and Jn numbers in the table’s “Element” column  
correspond to the locations with the same numbers in Figure 3-1.)  
Table 3-1. User-configurable options.  
Element  
Function  
Possible  
Settings  
Standard  
Factory  
Setting  
SW3  
BAUD RATE  
dial  
Select the data rate in kilobits per second.  
Opt. 1  
0-256  
1-192  
2-144  
3-128  
4-115.2*  
5-112  
6-96  
7-72  
8-64  
64 kbps  
9-57.6*  
A-56  
B-48  
C-38.4*  
D-32  
E-28.8  
F-19.2*  
*Async/  
sync baud  
rate  
J1  
V54 DIS  
Enable or disable requests for V.54 digital  
loopback tests from the remote line driver.  
DIS  
EN  
EN (enabled)  
ON  
jumper  
J2  
Select the transmit-carrier mode. When you  
set this jumper to “ON,” transmit carrier is  
constantly ON. When you set this jumper to  
jumper to “CNTRL,” transmit carrier is ON only  
when RTS is high.  
CNTRL  
ON  
CARRIER  
jumper  
Use the CNTRL setting for multipoint  
applications.  
J3  
XMT CLK  
jumper  
Select the source of the transmit timing signal:  
internal clock, external clock (from DTE), or  
receive clock (from remote unit). Do not select  
the ASY (asynchronous, no clock) setting.  
INT  
INT (Internal)  
EXT  
RCV  
ASY  
SW2  
Data-format  
DIP switch  
(This switch only comes into play when ASY  
[asynchronous] is selected on jumper J3. ASY  
should never be selected on this unit, so the  
settings of this switch are irrelevant.)  
17  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Table 3-1 (continued). User-configurable options.  
Element  
Function  
Possible  
Settings  
Standard  
Factory  
Setting  
J4  
RTS-CTS  
DLY jumper  
Select the delay in milliseconds that  
occurs during RTS-to-CTS transitions.  
Do not select 0 for multipoint applications.  
0
9
70  
9 ms  
J5  
V54 DLY  
jumper  
Turn V.54 delay ON or OFF. When you turn  
it ON, V.54 delay prevents multiple loopback  
of tail-end circuits.  
ON  
OFF  
OFF  
J6  
SW. EN.  
jumper  
Enable or disable the DIG, ANA, and REM  
loopback-control buttons on the unit’s front  
panel.  
ON  
OFF  
ON (enabled)  
J7  
Enable or disable electronic control of  
remote digital loopback testing through the  
DTE interface.  
EN  
DIS  
EN (enabled)  
EN (enabled)  
RLB DTE**  
jumper  
J8  
Enable or disable electronic control of  
local analog loopback testing through the  
DTE interface.  
EN  
DIS  
ALB DTE**  
jumper  
J9  
RCV LVL  
Select the level (in dBm) of receive  
input from the line.  
-6  
0
0 dBm  
jumper  
J10  
RCV IMP  
jumper  
Select the receive-line impedance. In  
multipoint applications, it is advisable to  
set the master modem and the last modem  
in the line to 150 , and all others to HIGH.  
150 []  
HIGH  
150 ohms  
J11  
RPF.  
Enable or disable the remote power  
failure feature.  
ON  
OFF  
ON  
jumper  
J12  
XMT LVL  
Select the level (in dBm) of transmit  
output to the line.  
-6  
0
0 dBm  
jumper  
J13  
XMT IMP  
jumper  
Select the transmit-line impedance in  
ohms. In multipoint applications, it is a  
good idea to set the master modem to  
“LOW.”  
150 []  
LOW  
150 ohms  
J14  
CHASS  
jumper  
Set to CON to connect signal ground to  
chassis ground. Set to DIS to keep the  
two grounds isolated from each other.  
DIS  
CON  
CON (connected)  
**NOTES:  
If the DTE does not provide the test pins for analog and remote loopback, the ALB DTE  
and RLB DTE jumpers must be always set to DIS.  
18  
 
CHAPTER 3: Configuration  
Figure 3-1. Layout of the 256-kbps Line Driver circuit board.  
19  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
When you have everything at least tentatively decided, take these steps to set the  
unit’s internal controls.  
CAUTION!  
Disconnect the standalone line driver from the power line before  
removing it from its housing.  
WARNING: HIGH VOLTAGE!  
Any adjustment, maintenance, and repair of the open instrument under  
voltage should be avoided as much as possible, and, when inevitable,  
should be carried out only by a skilled person who is aware of the  
hazard involved. Capacitors inside the instrument may still be charged  
even after the instrument has been disconnected from the power  
source.  
1. Disconnect the AC power cord from the AC mains outlet.  
2. Unscrew the two rear-panel screws until the rear panel becomes loose. This  
releases the unit’s “drawer” mechanism; now you can pull the screws as if they  
were the knobs on a drawer and expose or remove the unit’s circuit board.  
3. Identify the control(s) (refer to Figure 3-1).  
4. Move the control(s) to your desired position(s).  
5. Replace the circuit board and screw the rear-panel screws back in.  
20  
 
CHAPTER 4: Installation  
4. Installation  
4.1 Installing the Standalone Version in 19-Inch Racks  
4.1.1 OVERVIEW  
The 256-kbps Line Driver standalone version can be installed in 19-inch racks. It is  
1U (1.75", 4.4 cm) high and is slightly less than half as wide as the available  
mounting area.  
Two rack-adapter kits are available as special quotes: One kit provides the  
hardware necessary to install a single unit, and the other provides the hardware  
necessary to install two units side by side. Sections 4.1.2 and 4.1.3 provide step-by-  
step instructions for installation of single or dual units.  
CAUTION!  
Disconnect the units from AC power while performing the following  
procedures.  
4.1.2 INSTALLING A SINGLE UNIT IN A 19-INCH RACK  
The rack-adapter kit for single-unit installation includes one short bracket and one  
long bracket. The brackets are fastened with screws to the two side walls of the  
case, as shown in Figure 4-1.  
To prepare the standalone line driver for rack installation, attach the two brackets  
to the sides of the unit. Do this by inserting screws and flat washers into the two  
holes at the front of each side of the line driver (nuts are already in place inside  
the unit).  
After attaching the brackets, install the unit in your 19-inch rack by fastening the  
brackets to the rack’s side rails with four screws (not included in the kit), two on  
each side.  
21  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Figure 4-1. Installing a single unit in a 19-inch rack.  
4.1.3 INSTALLING TWO STANDALONE UNITS IN A 19-INCH RACK  
The adapter kit includes two long side rails (one for each unit), which slide into  
each other to fasten the units together, and two short side brackets, which hold the  
two line drivers side by side in a 19-inch rack. Refer to Figure 4-2 when you  
perform the following procedure:  
1. Fasten one long side rail to each standalone line driver—one rail on the right  
side of one unit, the other rail on the left side of the other unit—using the  
four included screws and flat washers. The rails must be attached so that they  
“oppose” each other: The narrow flange of the first rail must face the wide  
flange of the second rail.  
2. Using four included screws and flatwashers for each bracket, attach the two  
short brackets to the vacant sides of the standalone line drivers.  
3. Slide the two line drivers’ side rails into each other, fastening the two units  
together.  
22  
 
CHAPTER 4: Installation  
4. Secure the included plastic caps to the ends of the rails, to protect the rail  
ends and prevent the units from moving.  
5. You can now use four screws (not supplied with the kit), two on each side, to  
fasten the assembled units to the side rails of the 19-inch rack.  
Figure 4-2. Installing two units in a 19-inch rack.  
23  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
4.2 Installing the 256-kbps Line Driver Rackmount Card Version  
THE RACKNEST 2/14 ILLUSTRATED  
You will be installing the line driver card in the RackNest 2/14 as shown  
in Figure 4-3. The front and rear panels of the RackNest are shown  
in Figure 4-4; the numbered connectors, controls, and indicators  
are described in Table 4-1.  
Figure 4-3. Installing a card in the RackNest 2/14.  
24  
 
CHAPTER 4: Installation  
ON  
4
3
2
1
6
GND  
RCV  
XMIT  
5
7
Figure 4-4. The RackNest 2/14 illustrated.  
25  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Table 4-1. Descriptions of RackNest 2/14 components.  
Item  
Control, Indicator, or Connector  
Function  
1
Card Slots  
Slots for installation of compatible cards  
(slot no. 1 located at the left-hand side).  
Unused slots are closed with blank  
panels.  
2
Power-Supply Module  
Provides power to modules installed in  
the enclosure.  
3
4
ON Indicator  
Lights when power supply is operating.  
Chassis-Ground Terminal  
Connector for attaching other grounds,  
devices, etc., to the RackNest’s chassis  
ground (optional).  
5
6
Power Connector  
Power connector with integral fuse.  
Main Channel Connectors (J1) DB25 connectors for the module DTE  
connection.  
7
4-Wire Terminal Blocks (TB1)  
For connection of 4-wire lines. Each  
modem card has a separate terminal-  
block connector.  
26  
 
CHAPTER 4: Installation  
After you install the RackNest 2/14 in your 19" rack (refer to the RackNest’s  
manual), take these steps to install a line driver card in the RackNest:  
1. Insert the card into an empty slot on the RackNest (see Figure 4-3). Do  
not use excessive force. If the card does not go in easily, remove the card,  
realign it with the RackNest’s enclosure guides, and push it into place.  
NOTE  
When the RackNest 2/14 is ON, personnel are not exposed to any voltage  
over 30V on any card or accessible area of the nest. Still, take all  
reasonable precautions to avoid electric shock.  
2. Tighten the nut on the top of the card.  
3. Push the bottom of the card as far into the RackNest as it will  
comfortably go, to ensure that its card-edge connector makes full contact  
with the RackNest’s.  
4. Run an appropriate cable from your DTE to the corresponding DB25  
connector (“J1”) on the back of the RackNest:  
ME445C-530 (RS-530) units: You can use standard RS-530 (DB25 male-  
to-male) cable. Refer to Table 4-2 for more information.  
ME445C-35 (V.35) units: Either this cable needs to be specially pinned  
(see Table 4-3) and have a DB25 male connector at the RackNest end  
and an M/34 male connector at the DTE end, or you need to use a  
correctly pinned, short DB25-male-to-M/34-female cable or similar  
adapter to patch between the V.35 (M/34 male-to-male) cable and the  
RackNest’s DB25 connector. Call Black Box for a quote on this type of  
cable.  
ME445C-X21 (X.21) units: Either this cable needs to be pinned for  
RS-530 to X.21 (see Table 4-5) and have a DB25 male connector  
at the RackNest end and a DA15 (“DB15”) male connector at the DTE  
end, or you need to use a correctly pinned, short DB25-male-to-DA15-  
female cable or similar adapter to patch between the X.21 (DA15  
male-to-male) cable and the RackNest’s DB25 connector. Call Black  
Box for a quote on this type of cable.  
5. If you haven’t already done so, install the remote RackNest 2/14. Repeat  
steps 1 through 4 at the remote site.  
27  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
6. Run twisted-pair cable between the local and remote cards. Attach one  
pair of wires to the corresponding XMT terminals (“TB1”) on the back of  
the local RackNest and the corresponding RCV terminals on the remote  
RackNest; attach the other pair of wires to the RCV terminals on the local  
RackNest and the XMT terminals on the remote RackNest. (It doesn’t  
matter which wire in each pair goes to which terminal in each pair; the  
cards autosense parity.) If you’re using a ground wire, attach it to the GND  
terminal on one RackNest (not both of them!)  
28  
 
CHAPTER 4: Installation  
Table 4-2. Pinout of the RackNest 2/14’s DB25 connector when  
ME445C-530 is installed or RS-530 standalone’s DB25 connector.  
SIGNAL  
NAME (ABBREV.)  
ITU-TSS LEAD DB25  
CIRCUIT TYPE  
PIN  
Shield (SHD)  
101  
102  
1
Signal Ground (SGND)  
Transmitted Data (TD)  
7
103  
104  
105  
106  
107  
108  
109  
113  
114  
115  
A
B
2
14  
Received Data (RD)  
Request to Send (RTS)  
Clear to Send (CTS)  
A
B
3
16  
A
B
4
19  
A
B
5
13  
DCE Ready (DCR)  
a.k.a. Data Set Ready (DSR)  
A
B
6
22  
Data Terminal Ready (DTR)  
A
B
20  
23  
Received Line Signal Detector (RLSD),  
a.k.a. Carrier Detect (CD)  
A
B
8
10  
Transmitter Sig. Elem. Timing (DTE Source)  
(TSETT), a.k.a. External Clock (EXTC)  
A
B
24  
11  
Transmitter Sig. Elem. Timing (DCE Source)  
(TSETC), a.k.a. Transmit Clock (TC)  
A
B
15  
12  
Receiver Sig. Elem. Timing (DCE Source)  
(RSETC), a.k.a. Receive Clock (RC)  
A
B
23  
22  
Remote Loopback (RL)  
Local Loopback (LL)  
Test Mode (TM)  
140  
141  
142  
21  
18  
25  
29  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Table 4-3. Pinout of the RackNest 2/14’s DB25 connector  
when ME445C-35 is installed.  
SIGNAL  
NAME (ABBREV.)  
ITU-TSS  
LEAD DB25  
M/34  
CIRCUIT TYPE (RACK- (NORM.  
NEST)  
PIN  
V.35)  
PIN  
Frame (Protective) Ground (FGND)  
Signal Ground (SGND)  
Send Data (SD)  
101  
102  
103  
1
7
A
B
A
B
9
11  
P
S
Receive Data (RD)  
104  
A
B
12  
13  
R
T
Request to Send (RTS)  
Clear to Send (CTS)  
105  
106  
107  
108  
109  
4
5
C
D
E
H
F
Data Set Ready (DSR)  
Data Terminal Ready (DTR)  
6
20  
8
Received Line Signal Detector (RLSD),  
a.k.a. Carrier Detect (CD)  
Serial Clock Transmit External (SCTE),  
a.k.a. External Clock (EXTC)  
113  
114  
115  
A
B
19  
16  
U
W
Serial Clock Transmit (SCT),  
a.k.a. Transmit Clock (TC)  
A
B
14  
10  
Y
AA, a  
Serial Clock Receive (SCR),  
a.k.a. Receive Clock (RC)  
A
B
23  
22  
V
X
Remote Digital Loopback (RL)  
Local Analog Loopback (LL)  
Test Mode (TM)  
140  
141  
142  
21  
18  
25  
HH, h*  
JJ, j*  
KK, k*  
*Black Box often assigns these signals to these M/34 pins, but your DTE might  
use different pins (if it supports these signals at all). Consult your DTE’s manual.  
30  
 
CHAPTER 4: Installation  
Table 4-4. Pinout of the V.35 standalone’s M/34 connector.  
SIGNAL  
NAME (ABBREV.)  
ITU-TSS  
CIRCUIT  
LEAD  
TYPE  
V.35  
PIN  
Frame (Protective) Ground (FGND)  
Signal Ground (SGND)  
Send Data (SD)  
101  
102  
103  
A
B
A
B
P
S
Receive Data (RD)  
104  
A
B
R
T
Request to Send (RTS)  
Clear to Send (CTS)  
105  
106  
107  
108  
109  
C
D
E
H
F
Data Set Ready (DSR)  
Data Terminal Ready (DTR)  
Received Line Signal Detector (RLSD),  
a.k.a. Carrier Detect (CD)  
Serial Clock Transmit External (SCTE),  
a.k.a. External Clock (EXTC)  
113  
114  
115  
A
B
U
W
Serial Clock Transmit (SCT),  
a.k.a. Transmit Clock (TC)  
A
B
Y
AA  
Serial Clock Receive (SCR),  
a.k.a. Receive Clock (RC)  
A
B
V
X
Remote Digital Loopback (RL)  
Local Analog Loopback (LL)  
Test Mode (TM)  
140  
141  
142  
HH  
JJ  
KK  
31  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Table 4-5. Pinout of the RackNest 2/14’s DB25 connector when  
ME445C-X21 is installed.  
SIGNAL  
ITU-TSS  
LEAD DB25  
DA15  
NAME (ABBREV.)  
CIRCUIT TYPE (RACK- (NORM.  
NEST)  
PIN*  
X.21)  
PIN  
Shield (n/a)  
101  
102  
1
7
1
8
Ground (G)  
a.k.a. Signal Ground (SGND)  
Transmit (T)  
Receive (R)  
103  
104  
105  
109  
113  
114  
A
B
2
14  
2
9
A
B
3
16  
4
11  
Control (C)  
a.k.a. Request to Send (RTS)  
A
B
4
19  
3
10  
Indication (I)  
a.k.a. Carrier Detect (CD)  
A
8
10  
5
12  
RS-530: Transmitter Signal Element  
Timing (DTE Source) (TSETT)†  
A
B
24  
11  
7†  
14†  
Signal Timing (S)  
A
B
15  
12  
6
13  
*This pinout follows the TIA RS-530 standard.  
†Standard X.21 does not support an external clock, and specifies that DA15 Pins 7  
and 14 should be used for the Byte Timing (B) A and B signals. Because Byte  
Timing is hardly ever used, but an external clock is often necessary for today’s  
data communication, many Black Box devices are designed to this modified  
specification in which the RS-530 external-clock signal replaces Byte Timing.  
32  
 
CHAPTER 4: Installation  
4.3 Connecting Data Cables  
After you set the standalone line driver’s internal controls, it’s ready to be cabled  
for operation.  
Its electrical connectors are located on its rear panel. These consist of a female  
V.35 interface connector labeled “DTE,” a 5-screw terminal block, and an IEC 320  
AC inlet that contains an integral fuse compartment.  
The V.35 interface connector, a 34-pin M-block female, carries input/output data,  
clock signals, and control signals between the line driver and the DTE or DCE  
(refer to Table 4-4).  
The terminal block has five screws for connecting transmit and receive lines—the  
transmit pair where XMT is indicated (for data output from the unit), the receive  
pair where RCV is indicated (for data input to the unit), and a drain wire from the  
cable shield, if you are using shielded cable, where GND is indicated. The XMT  
and RCV pairs are not sensitive to polarity.  
Connect power and data cables to the line driver as described in the following  
subsections.  
4.3.1 POWER CONNECTION  
The power connection provides AC voltage to the line driver.  
To make this connection on the 115-VAC (ME444A-R3) models, first attach the  
IEC 320 female outlet of the included power cord to the IEC 320 male inlet on the  
standalone line driver’s rear panel.  
To make this connection on the 230-VAC (ME444AE-R3) models, first attach the  
IEC 320 female outlet of an appropriate power cord to the IEC 320 male inlet on  
the standalone line driver’s rear panel. (This power cord must have a plug on the  
other end that will fit the site’s mains outlets.)  
WARNING!  
BEFORE PLUGGING THIS UNIT INTO AN OUTLET OR OTHER LIVE  
POWER SOURCE, make sure its protective earth contact is connected to  
the protective conductor of the (mains) power cord. The mains plug  
must be inserted only in a socket outlet provided with a protective earth  
contact. The protective action must not be negated by use of an  
extension cord (power cable) without a protective (grounding)  
conductor.  
If the line driver’s fuse blows (opens), make sure that you replace it only with a  
33  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
fuse rated for the required amount of current. You must avoid using repaired fuses  
or short-circuiting the fuse holders. The fuse, and one replacement fuse, are  
located in the top part of the mains connector on the line driver’s rear panel. The  
nominal current value of the fuse is 0.125 A for 230-VAC operation or 0.25 A for  
115-VAC operation.  
Whenever it is likely that the protection offered by the fuse has been impaired, the  
unit must be made inoperative and secured against any unintended operation.  
After you have attached the power cord and have made sure that the cord is  
properly grounded, you can plug the power cord into a working mains outlet.  
CAUTION!  
The unit has no power switch. It starts operating as soon as power  
of the proper type is applied to its POWER connector.  
4.3.2 LINE CONNECTION  
The LINE connection provides an interface for the TX and RX signals between  
pairs of line drivers. To make this connection, attach the line wires to the terminal  
block on the line driver this way:  
• XMT + (remote line driver) to RCV + (local unit);  
• XMT – (remote unit) to RCV – (local unit);  
• RCV + (remote unit) to XMT + (local unit);  
• RCV – (remote unit) to XMT – (local unit);  
• Optional: Shield or drain wire (line cable) to ground (local line driver—the  
rightmost terminal).  
All connections are made on the back of the line driver.  
4.3.3 DTE CONNECTION  
The interface (DTE) connector provides an interface for input/output data, as  
well as clock and control signals, between the line driver and a V.35 DTE or DCE.  
This connector is a standard 34-pin M-block (“M/34”) female. The pinout of this  
connector is shown in Table 4-4.  
34  
 
CHAPTER 4: Installation  
To connect the line driver to a V.35 DTE or DCE, use an appropriate cable that is  
pinned correctly (straight-through for DTE, properly crossed for DCE). Run this  
cable from the other device to the line driver and attach it to the line driver’s  
interface connector.  
Your line driver should now be ready for continuous operation.  
35  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
5. Operation  
This chapter contains a list of the controls and indicators and their functions, as  
well as a brief description of how to operate the unit. Installation procedures must  
be completed and checked before you attempt to operate the line driver.  
5.1 Controls and Indicators  
The front panel of the standalone line driver is shown in Figure 5-1 below. The  
front panel of the rackmount card line driver is shown in Figure 5-2. It contains all  
of the unit’s external controls and indicators. The functions of the controls are  
described in Table 5-1, and the meanings of the indicators are described in Table  
5-2. In each of these tables, the letters and numbers under the heading “Item”  
correspond to the letters and numbers in Figure 5-1 or 5-2.  
DIG  
ANA  
REM  
PATT  
PWR RTS  
TD  
RD DCD TEST ERR  
1
2
3
4
5
6
7
A
B
C
D
Figure 5-1. The front panel of the standalone line driver.  
36  
 
CHAPTER 5: Operation  
PWR  
RTS  
TD  
1
2
4
3
RD  
DCD  
5
TEST ERR  
6
7
RPF  
E
B
DIG  
A
ANA  
REM  
PATT  
C
D
Figure 5-2. The front panel of the rackmount card line driver.  
Table 5-1. The controls.  
The Item labels in this table correspond to those in Figures 5-1 and 5-2.  
ITEM  
A
CONTROL  
DIG  
FUNCTION  
Pressing the local digital loopback button causes the local LDM-MR256 to  
loop received data and clock to its transmitter. Data Set Ready goes low.  
B
C
D
ANA  
Pressing the local analog loopback (V.54 Loop 3) button causes the local  
LDM-MR256 to loop its transmitter output back to its receiver. This  
loopback may also be activated from the DTE when the “ALB DTE” jumper  
is set to EN.  
REM  
PATT  
Pressing the remote digital loopback (V.54 Loop 2) switch causes the  
remote LDM-MR256 to loop received data and clock to its transmitter.  
Data Set Ready goes low. This loopback may be also activated from the  
DTE when the “RLB DTE” strap is set to EN.  
Pressing the PATT button causes the LDM-MR256 to send and receive a  
511 test pattern. If errors are encountered, the ERR LED becomes  
steadily lit or blinks. Receive Data and Clear to Send go low. Note: The  
unit’s “CARRIER” jumper should be set to ON; if it is set to CNTRL, the  
RTS signal must be high.  
E
RPF  
Remote Power Failure resets the ERR/RPF LED.  
37  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
Table 5-2. The indicators.  
The item numbers in this table correspond to Figures 5-1 and 5-2.  
ITEM  
INDICATOR  
PWR  
FUNCTION  
Green LED is on when power is on.  
1
2
3
RTS  
Yellow LED is on when terminal activates Request to Send.  
TD  
Yellow LED is on when steady SPACE is being transmitted. It flickers  
when data is transmitted.  
4
RD  
Yellow LED is on when steady SPACE is being received. It flickers  
when data is received.  
5
6
7
DCD  
TEST  
ERR  
Yellow LED is on when a valid receive signal is present.  
Red LED is on when the LMD-MR256 is in any of the loopback modes.  
LED goes ON when PATT switch is activated and then dims. If there are  
errors in the test pattern, the LED blinks or remains ON.  
5.2 Operating Procedure  
The line driver operates entirely unattended, although we recommend that you  
monitor its LEDs occasionally. To turn the unit off, you must unplug its power  
cord from the outlet—it has no power switch.  
If you want to reconfigure the line driver for a different type of operation, make  
very sure to unplug the unit first. After the unit is powered down, change the  
settings of its internal controls as necessary, following the instructions in  
Section 3.3.  
38  
 
CHAPTER 6: Troubleshooting  
6. Troubleshooting  
This chapter explains system-test and fault-isolation procedures.  
The line driver provides local loopback and remote digital loopback in compliance  
with the V.54 standard. Unless you disable them, the unit’s loopback tests can be  
activated manually from the unit’s front panel, and the local analog and remote  
digital loopbacks can be activated electronically through the DTE connection.  
6.1 Loop Tests  
The loop-test buttons (DIG, ANA, and REM) and LEDs built into the line driver  
allow you to rapidly check the unit, the attached cables, and the attached DTEs.  
Use the test procedures described in this chapter to verify normal system operation  
and to isolate faulty equipment if a failure occurs. (Before testing the operation of  
the system equipment and line circuits, make sure that all devices are turned on  
and are properly configured.)  
6.2 The Bit-Error-Rate Tester (BERT)  
You can activate the line driver’s internal Bit Error Rate Tester in any diagnostics  
test in which the transmitted test pattern is looped back to the BERT for  
comparison. An example is shown in Figure 6-1 on the next page.  
The line driver is also capable of operating opposite any 511 BERT tester. When  
you use one line driver opposite another, either with one or both PATT buttons  
pressed (see Figure 6-2) or with an external BERT transmitting the same V.52 (511-  
bit) pattern, you can test the complete link. To activate the BERT, press the PATT  
button. The ERR LED will light momentarily, 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).  
NOTE  
For the line driver’s BERT to operate correctly, the CARRIER jumper  
must be set to ON or the RTS signal must be high.  
While PATT is pressed, the V.35 interface is functionally disconnected.  
39  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
PATT  
PRESSED  
XMT  
PATTERN  
GENERATOR  
PATTERN  
TESTER  
RCV  
ERROR  
ASM-20  
Figure 6-1. BERT using loops.  
DEPRESSED  
(DISCONNECTS  
EXTERNAL DTE)  
PATT  
DEPRESSED  
RCV  
XMT  
PATTERN  
GENERATOR  
PATTERN  
TESTER  
ERROR  
DTE  
PATTERN  
TESTER  
PATTERN  
GENERATOR  
ERROR  
Figure 6-2. Two line drivers doing end-to-end BERT.  
40  
 
CHAPTER 6: Troubleshooting  
6.3 The Modem Self-Test  
To verify that the line driver itself is operating correctly, initiate the modem self-  
test by pressing the PATT and ANA buttons (refer to Figure 6-3 below):  
1. Press ANA to start local analog loopback. Both the TEST and DCD LEDs  
should light. If the DCD LED doesn’t light, make sure that the RTS signal is  
not OFF (low) while the CARRIER jumper is OFF.  
2. Press PATT to begin test-pattern transmission. Verify that the TEST and DCD  
LEDs are still lit and that the ERR LED lights briefly.  
3. If the ERR stays lit or continues to flicker after the initial flash, the line driver  
is faulty; call Black Box to arrange for repair or replacement. Otherwise, the  
unit passes the test; restore all of the buttons to their normal positions.  
PATT  
DEPRESSED  
ANA  
DEPRESSED  
PATTERN  
GENERATOR  
XMTR  
RCVR  
PATTERN  
TESTER  
ERROR  
Figure 6-3. Modem self-test.  
6.4 Local Analog Loopback  
Activate the local analog loopback test by pressing the ANA button or by raising  
the level of the Local Loopback signal received by the line driver’s V.35 connector  
(Pin JJ). This test checks the performance of the local line driver, the local DTE,  
and the connections between them. Perform this test separately at the local and  
remote sites (refer to Figure 6-4 on the next page):  
1. Press ANA or raise Local Loopback to start local analog loopback. The  
TEST LED should light. The line driver’s G.703 transmit output should be  
connected to its own receiver.  
41  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
2. Verify that the DTE is operating properly and can be used for a test.  
3. Perform the test using one of these methods:  
• Send data from the DTE and check the echoed data stream.  
• Hook up an external Bit Error Rate Test (BERT) unit in place of the DTE.  
• Use the 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).  
4. Repeat Steps 1 through 3 at the remote site.  
5. If the BERT tests show no errors, but the data echoed back to either DTE is  
bad, check the DTE and the cable connecting it to the line driver—one of  
them is faulty.  
6. After the test is complete or the fault has been corrected, restore the ANA  
button to its normal position. Proceed with the digital loopback tests.  
ANA  
DEPRESSED  
DATA  
XMTR  
RCVR  
CLK  
DTE  
LINE  
CLK  
DATA  
Figure 6-4. Local analog loopback.  
42  
 
CHAPTER 6: Troubleshooting  
6.5 Remote Digital Loopback  
Activate the remote digital loopback test by pressing the REM button or by raising  
the level of the remote loopback signal received by the line driver’s V.35 connector  
(Pin HH). This test involves creating an outbound loopback at the remote line  
driver (see Figure 6-5 on the next page). The test checks the performance of the  
local and remote units and the line between them:  
1. Press REM or raise remote loopback; the local line driver will signal the  
remote unit to start remote digital loopback. The TEST LED should light on  
both units. The remote 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 Bit Error Rate Test (BERT) unit in place of the local  
DTE; or  
• Use the local 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, there is a problem somewhere in the communication line between the  
units.  
4. After the test is complete or the fault has been corrected, restore the REM  
button to its normal position. Proceed with local digital loopback.  
43  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
REM  
DEPRESSED  
DATA  
XMTR  
RCVR  
RCVR  
XMTR  
CLK  
LOCAL  
DTE  
REMOTE  
DTE  
CLK  
DATA  
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  
 
CHAPTER 6: Troubleshooting  
4. After the test is complete or the fault has been corrected, restore the DIG  
button to its normal position.  
DIG  
DEPRESSED  
DATA  
XMTR  
RCVR  
RCVR  
XMTR  
CLK  
LOCAL  
DTE  
REMOTE  
DTE  
DATA  
CLK  
Figure 6-6. Local digital loopback.  
6.7 Calling Black Box  
If you determine that your line driver 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. The problem might be solvable over the phone.  
Before you do, make a record of the history of the problem. We will be able to  
provide more efficient and accurate assistance if you have a complete description,  
including:  
• the nature and duration of the problem.  
• when the problem occurs.  
• the components involved in the problem.  
• any particular application that, when used, appears to create the problem or  
make it worse.  
45  
 
256-KBPS LINE DRIVER (V.35, RS-530, OR X.21)  
6.8 Shipping and Packaging  
If you need to transport or ship your line driver:  
• Package it carefully. We recommend that you use the original container.  
• If you are shipping the line driver for repair, make sure you include its power  
cord. If you are returning the LDM-MR256, make sure you include its manual  
as well. Before you ship, contact Black Box to get a Return Authorization (RA)  
number.  
46  
 
APPENDIX: Maximum Distances  
Appendix: Maximum Distances  
The maximum distance that a pair of line drivers can communicate across will  
vary depending on the data rate and the thickness (gauge) of the wires. In  
multipoint applications, it will also vary depending on the number of slaves  
on the line. Approximate maximum distances for different combinations of  
these factors are listed in the tables below. Please be aware that these numbers  
are only approximations; the distances shown might not be attainable for all  
applications. Also, maximum distances will always be less than those listed  
when line drivers are used in noisy environments.  
Table A-1. Approximate range.  
Baud Rate  
(kbps)  
19-AWG  
(0.8 mm)  
22-AWG  
(0.6 mm)  
24-AWG  
(0.5 mm)  
26-AWG  
(0.4 mm)  
km  
miles  
km  
miles  
km  
miles  
km  
miles  
256  
192  
144  
128  
115.2*  
112  
96  
3.7  
6
2.3  
3.7  
2.85 1.8  
4.5 2.8  
6.75 4.2  
7.3 4.5  
7.65 4.8  
2.25  
3.5  
4.5  
5
1.4  
2.2  
2.8  
3.1  
3.3  
3.4  
3.7  
3.9  
4.7  
5
1.9  
2.7  
3.4  
3.6  
3.8  
4
1.2  
1.7  
2.1  
2.2  
2.4  
2.5  
2.6  
2.7  
3.3  
3.5  
3.5  
3.6  
3.7  
3.9  
3.9  
4.3  
10.6  
12.4  
12.8  
12.8  
13  
6.6  
7.7  
8
5.25  
5.5  
6
8
8
5
8.1  
8.3  
9.4  
5.2  
5.8  
6.8  
4.15  
4.3  
5.3  
5.6  
5.6  
5.8  
6
72  
15  
9.3  
6.25  
7.5  
8
64  
17.6  
18.8  
18.8  
19.4  
20  
10.9  
11.7  
11.7  
12.1  
12.4  
12.7  
12.7  
14.3  
11  
57.6*  
56  
11.75 7.3  
11.75 7.3  
8
5
48  
12.2  
12.5  
12.85  
12.85  
14  
7.6  
7.8  
8
8.25  
8.5  
8.75  
8.75  
9.75  
5.1  
5.3  
5.4  
5.4  
6.1  
38.4*  
32  
20.5  
20.5  
23  
6.2  
6.2  
7
28.8*  
19.2**  
8
8.7  
*Async baud rate  
**Sync/async baud rate  
47  
 
© Copyright 2004. Black Box Corporation. All rights reserved.  
1000 Park Drive  
Lawrence, PA 15055-1018  
724-746-5500  
Fax 724-746-0746  
 

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