Black Box ME243A-F User manual

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 [phone]
Mailing address: Black Box Corporation, 1000 Park Drive, Lawrence, PA 15055-1018
Web site: www.blackbox.com • E-mail: [email protected]
DECEMBER 1997
ME243A-F
V.35 Sync Modem Eliminator
V.35 Sync
Modem Eliminator

1
FCC AND DOC/MDC RFI STATEMENTS
FEDERAL COMMUNICATIONS COMMISSION
AND
INDUSTRY CANADA
RADIO FREQUENCY INTERFERENCE STATEMENTS
This equipment generates, uses, and can radiate radio-frequency energy, and if not
installed and used properly, that is, in strict accordance with the manufacturer’s
instructions, may cause interference to radio communication. It has been tested
and found to comply with the limits for a Class A computing device in accordance
with the specifications in Subpart B of Part 15 of FCC rules, which are designed to
provide reasonable protection against such interference when the equipment is
operated in a commercial environment. Operation of this equipment in a
residential area is likely to cause interference, in which case the user at his own
expense will be required to take whatever measures may be necessary to correct
the interference.
Changes or modifications not expressly approved by the party responsible
for compliance could void the user’s authority to operate the equipment.
This digital apparatus does not exceed the Class A limits for radio noise emission from
digital apparatus set out in the Radio Interference Regulation of Industry Canada.
Le présent appareil numérique n’émet pas de bruits radioélectriques dépassant les limites
applicables aux appareils numériques de la classe A prescrites dans le Règlement sur le
brouillage radioélectrique publié par Industrie Canada.
TRADEMARKS USED IN THIS MANUAL
Any trademarks mentioned in this manual are acknowledged to be the property of the
trademark owners.

2
V.35 SYNC MODEM ELIMINATOR
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.

3
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.

4
V.35 SYNC MODEM ELIMINATOR
Contents
Chapter Page
1. Specifications ............................................................................................. 5
2. Introduction ............................................................................................... 7
3 Configuration ............................................................................................. 8
3.1 Opening the Housing ......................................................................... 8
3.1.1 Opening the Middle Section .................................................... 9
3.1.2 Opening the Top of the Port-B End ...................................... 10
3.2 Setting the DIP Switch ...................................................................... 11
3.3 Setting the Jumpers .......................................................................... 13
3.4 Reclosing the Housing ...................................................................... 15
3.4.1 Closing the Top of the Port-B End ........................................ 15
3.4.2 Closing the Middle Section .................................................... 15
4. Installation and Operation ...................................................................... 16
5. Troubleshooting ...................................................................................... 18
5.1 Calling Black Box .............................................................................. 18
5.2 Shipping and Packaging ................................................................... 18
Appendix: Block Diagram .............................................................................. 19

5
CHAPTER 1: Specifications
1. Specifications
Compliance — CE; FCC Part 15 Class A, DOC Class/MDC classe A
Interface — Serial ITU-TSS V.35
Protocol — Synchronous
Clock Source — Either internal for both ports or external for
Port A and recovered for Port B(user-selectable)
Flow Control — Transparent to software flow control; does not
support hardware flow control, but emulates RTS-to-
CTS delay of 0, 7, or 53 ms ±15% (user-selectable)
Operation — Point-to-point
Data Rate — 32, 48, 56, 64, 72, 112, 128, or 144 kbps (user-
selectable)
Maximum Distance — 300 ft. (91.4 m) from one attached DTE to the other
User Controls — (4) Internal:
(1) Four-position DIP switch for data rate;
(3) Jumpers for RTS/CTS delay, carrier control,
and clock source
Indicators — None
Connectors — (2) End-mounted M/34 (“34-pin M-block”) female
MTBF — 144,600 hours

6
V.35 SYNC MODEM ELIMINATOR
Maximum Altitude — 10,000 ft. (3048 m)
Temperature
Tolerance — 32 to 122˚F (0 to 50˚C)
Humidity
Tolerance — 5 to 95% noncondensing
Power — From the V.35 Interface on both ports: 5 VDC,
6 mA drawn from each port’s RTS and DTR
signals (Pins C and H); maximum total
consumption approximately 120 mW
Size — 0.8"H x 2"W x 3"D (2 x 5.1 x 7.6 mm)
Weight — 3.3 oz. (95 g, 0.2 lb., 0.1 kg)

7
CHAPTER 2: Introduction
2. Introduction
With our V.35 Synchronous Modem Eliminator (SME), two synchronous
hosts that are not farther apart than 300 ft. (91.4 m) can communicate with
each other for a fraction of the cost of a pair of high-speed modems. The V.35
SME supports synchronous data rates of 32, 48, 56, 64, 72, 112, 128, and 144
kbps, and can be configured to emulate dialup or leased-line service. Timing
can be set for internal or external clock, and all necessary data, clocking, and
control signals are supported.
The V.35 SME implements the V.35 electrical interface on two standard
M/34 (“34-pin M-block”) female connectors. The unit draws its power directly
from the Request to Send (RTS) and Data Terminal Ready (DTR) signal leads
(Pins C and H) on both ports, so no AC power or batteries are required.
You can configure the V.35 SME’s behavior in several other ways. For
example, you can set it to keep carrier constantly ON or to have carrier follow
RTS; you can also set it to immediately respond to RTS with CTS or to
emulate an RTS-to-CTS delay of 7 or 53 ms.

8
V.35 SYNC MODEM ELIMINATOR
3. Configuration
The V.35 Synchonous Modem Eliminator has seven internal user controls—
one four-position DIP switch and six jumpers—with which you can configure
the unit for a wide range of applications. This chapter tells you how to open,
set, and reclose the V.35 SME, and describes all of the unit’s possible
configuration settings (including its factory defaults).
3.1 Opening the Housing
Before you go any farther, answer these questions:
First, will your devices be using the V.35 SME’s internal clock, and do you
want carrier constantly ON and an RTS-to-CTS delay of 7 ms (the factory-
default settings for these options)? If not, you will need to open both the
middle portion and the top of the Port-B end of the unit’s housing: Skip
ahead and follow the directions in Sections 3.1.1 and 3.1.2.
Second, will your devices be communicating through the V.35 SME at
32 kbps (the factory-default data rate)? If not, you will need to open just the
middle portion of the unit’s housing: Skip ahead and follow the directions in
Section 3.1.1 only (do not do Section 3.1.2).
If you are satisfied with all of the factory-default settings, you don’t need to
configure the unit at all; skip ahead to Chapter 4.

9
CHAPTER 3: Configuration
3.1.1 O PENING THE
M IDDLE S ECTION
Carefully insert a screwdriver, knife, or other tool with a very thin flat blade
into the seam along the side of the middle part of the V.35 SME’s housing
(the section with the model- and lot-number stickers). Gently twist the tool
until the all-plastic top and bottom panels of this housing section begin to
pop apart. (You will probably hear a snapping noise; this is normal.) If they
don’t come all the way off, carefully pry them the rest of the way off with your
fingers. See Figure 3-1 below.
Figure 3-1. Removing the middle section.

10
V.35 SYNC MODEM ELIMINATOR
3.1.2 O PENING THE
T OP OF THE P ORT -B E ND
This is a tricky procedure, so follow these instructions very carefully. Now that
you have the middle section open, find the DIP switch. It is mounted in plain
view on top of the V.35 SME’s insides, in one corner of one of the unit’s
circuit boards; refer to Figure 3-3 on the next page. If you hold the unit so
that this DIP switch is in the lower left corner of the exposed area, the housing
panel you need to remove is the nearest one to the Switch, the one to its left. If
you look closely, you will see that this panel partially obscures a copyright
notice printed on the DIP switch’s circuit board, as well as the edge of this
board (the jumpers you need to get at are on the unit’s main board, beyond
and below this edge).
Figure 3-2. Removing the top panel on the Port-B end.
To remove this panel, you need to unscrew and remove the two screws that
hold it on. These are at the very end of the unit: They are the top two screws
in Port B’s M/34 connector (one in the upper left corner, one in the upper
right—see Figure 3-2 below). Use a long, thin flathead screwdriver to back
these screws out one at a time. As you unscrew each screw, try to hold the unit
with the opposite side of Port B angled upward, so that when the associated
nut and lug washer come loose, they fall into your hand rather than into the
adjacent hole in the V.35 SME’s housing. (If any of the nuts or washers should
happen to fall into the unit, don’t panic; they can be shaken through to the

11
CHAPTER 3: Configuration
open middle section and out of the unit without damaging it. Just make sure
to shake them out over a partitioned-off area of a counter, desktop, etc., so
that you don’t lose them if you miss catching them when they come out.)
Once you’ve removed both of these screws, firmly grip the housing panel
that has to come off and carefully pry it away from the rest of the unit. (You
will probably hear a snapping noise; this is normal.)
3.2 Setting the DIP Switch
As you can see, the V.35 SME’s four-position data-rate DIP switch is mounted
on an internal daughterboard. Figure 3-3 below shows the location of this
switch, the numbering of its individual switch positions, and the directions of
their ON and OFF settings relative to the rest of the unit.
Figure 3-3. The internal controls: The DIP switch.
ON
OFF
ON
1 2 3 4
Port
B
Port
A
Jumpers
DIP
Switch

12
V.35 SYNC MODEM ELIMINATOR
Move positions 1, 2, and 3 of this switch as necessary to select your desired
synchronous data rate. (Position 4 is reserved for future use.) Table 3-1 below
shows the V.35 SME’s possible data-rate settings.
Table 3-1. Data-Rate Settings
P. 1 P. 2 P. 3 Data Rate
Off Off Off 32 kbps (factory default)
On Off Off 48 kbps
Off On Off 56 kbps
On On Off 64 kbps
Off Off On 72 kbps
On Off On 112 kbps
Off On On 128 kbps
On On On 144 kbps

13
CHAPTER 3: Configuration
3.3 Setting the Jumpers
The V.35 SME also has three pairs of jumpers—JP1, JP2, and JP3—mounted
on its main circuit board (see Figure 3-4 below; the jumpers are shown in
their factory-default settings). Use these jumpers to independently set
clocking, carrier, and RTS/CTS delay for Ports A and B. (You will probably
have to use needle-nosed pliers to move the jumpers.)
Figure 3-4. The internal controls: The jumpers.
Notice that in each pair of jumpers, one jumper controls the setting of Port A
and the other controls that of Port B. Also notice that each jumper has three
possible settings: covering posts 1 and 2, covering posts 2 and 3, or “removed”
(usually left covering only a single post, so it doesn’t get lost). The detailed
descriptions of each jumper pair on the next page list all possible jumper settings.
JP3 1
2
3
JP1 1
2
3
JP2 1
2
3
Port
B
Port
A
Controls Port A Controls Port B
Jumpers
DIP
Switch

14
V.35 SYNC MODEM ELIMINATOR
JP3: Clock Source
The settings of the JP3 jumpers determine whether (a) both devices
connected to the V.35 SME use the SME’s internal clock or (b) the device on
Port A uses external clock and the device on Port B uses recovered (received)
clock. (Port A cannot be set for recovered clock; Port B cannot be set for
external clock. Do not set one port for internal clock and the other for
external or recovered clock; the system will not work.)
JP3 (Port A) Setting
On positions 1 and 2 Internal clock (factory default)
On positions 2 and 3 External clock
Removed (This setting is reserved for future use)
JP3 (Port B) Setting
On positions 1 and 2 Internal clock (factory default)
On positions 2 and 3 Recovered (received loopback) clock
Removed (This setting is reserved for future use)
JP1: RTS/CTS Delay
The settings of the JP1 jumpers determine the amount of delay after the V.35
SME detects RTS before it sends CTS in response. In order to emulate dialup
or leased-line modems, you can set either of these jumpers for 0 ms, 7 ms, or
53 ms of delay. The jumpers for Ports A and B can be configured
independently (that is, you can set them differently).
JP1 Setting
On positions 1 and 2 7-ms delay (factory default)
On positions 2 and 3 53-ms delay
Removed 0-ms delay (no delay, instant response)
JP2: Carrier Control
The settings of the JP2 jumpers determine whether the V.35 SME holds
carrier constantly ON or turns it ON and OFF in response to RTS. The
jumpers for Ports A and B can be configured independently (that is, you can
set them differently).
JP2 Setting
On positions 1 and 2 Carrier controlled by RTS
On positions 2 and 3 Carrier constantly ON (factory default)
Removed (This setting is reserved for future use)

15
CHAPTER 3: Configuration
3.4 Reclosing the Housing
Before you go any further, make absolutely sure the jumper settings are
correct, because the last thing you want to do is get the V.35 SME put back
together and then have to turn around and disassemble it again.
3.4.1 C LOSING THE T OP OF THE P ORT -B E ND
Take the housing panel that you removed in Section 3.1.2 and place it in
position to be reattached, with the “snap flanges” on either side of the panel
lined up flush against the matching flanges on the still-attached bottom panel.
When the panel is in the right position, grasp the Port B end of the V.35 SME
firmly on both sides and press the top and bottom panels together to snap the
top panel back into place.
Now take one of the two screws you removed in Section 3.1.2 and thread it
back into its screwhole in the M/34 connector. Push it in just far enough so
that its pointy end slightly protrudes from the other side of the hole. Now,
with a screwdriver holding the screw in place, fit the washer over the end of
the screw, then lay the nut on the end of the screw and turn the nut or the
screw just far enough for them to grip. (You might want needle-nosed pliers
for this step. If the washer and/or the nut slip through the adjacent hole and
into the V.35 SME, just carefully shake them out through the open middle
section of the unit onto your work surface and start over.) Now use a fingertip
to hold the nut in place and turn the screwdriver until the screw is securely
fastened. Repeat this process with the other screw.
3.4.2 C LOSING THE M IDDLE S ECTION
Take the top and bottom panels of the middle section of the V.35 SME’s
housing, which you removed in Section 3.1.1, and slide them back into
position to be reattached, with the “snap flanges” on either side of each panel
lined up flush against the matching flanges on the opposite panel. Then press
them together until they snap into place.

16
V.35 SYNC MODEM ELIMINATOR
4. Installation and Operation
Once the V.35 Synchronous Modem Eliminator is properly configured,
installation and operation are very simple. The V.35 SME draws all necessary
operating power from the V.35 interface, so it doesn’t need AC or battery
power. There is no ON/OFF switch; just like a cable, the unit should operate
transparently and continuously when the connected devices are turned ON
and communicating. To install the unit, take these steps:
1. Turn OFF the host (DTE) devices to which the V.35 SME is to be
connected.
2. If either of the host devices has a M/34 male V.35 port, you can plug the
V.35 SME directly into that device. Then connect the V.35 SME to the
other host device using a multipair cable. (If neither device has an M/34
male V.35 port, you’ll have to run multipair cable to both devices.) The
total cable length between the two devices must not exceed 300 feet
(91.4 m). Refer to Figure 4-1 below.
Remember that if one of the devices (rather than the V.35 SME) will be
supplying the clock signal, you need to orient the V.35 SME so that the
device configured for external clock is connected to Port A and the
device configured for recovered clock is connected to Port B.
Figure 4-1. A typical installation.
Sync Host A
(System can use clock from V.35 SME or Host A, but not from Host B.)
Port A
150 ft.
(45.7 m)
284 ft. (86.5 m)
134 ft.
(40.8 m)
Port B
V.35 SYNC MODEM
ELIMINATOR
(ME243A-F)
Sync Host B

17
CHAPTER 4: Installation and Operation
3. Turn ON both host devices. They should communicate normally as if
connected by a simple cable. If they do not communicate properly, first
make sure that all cabling is connected securely, then check the
configuration of the V.35 SME and of each host device: Which one is
supplying the clock? What’s the data-rate setting of each device? And so
on. If you’re still having trouble, contact Black Box for technical support
(see Section 5.1).

18
V.35 SYNC MODEM ELIMINATOR
5. Troubleshooting
5.1 Calling Black Box
If you determine that your V.35 Synchronous Modem Eliminator is
malfunctioning, do not attempt to alter or repair the unit. It contains no user-
serviceable parts. Contact Black Box Technical Support at [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.
• the results of any testing you’ve already done.
5.2 Shipping and Packaging
If you need to transport or ship your V.35 SME:
• Package it carefully. We recommend that you use the original container.
• If you are returning the V.35 SME, make sure you include everything your
received with it. Before you ship the unit back to us for whatever reason,
contact Black Box to get a Return Authorization (RA) number.

19
APPENDIX: Block Diagram
Appendix: Block Diagram
The figure below is a vastly simplified block diagram showing the general
layout of the V.35 Synchronous Modem Eliminator’s circuitry.
DCDA DCDB DSRA DSRB CTSA CTSB RTSA RTSB DTRA DTRB RDA- TDB- RDA+ TDB+ TDA- RDB- TDA+ RDB+ SGND SGND PGND PGND XTC+ XTC- TCA+ TCB+ TCA- TCB- RCA+ RCB+ RCA- RCB-
S
S
S
1 2 3
S
+V -V +5V -5V
RTS/CTS DELAY SELECT
CLOCK SOURCE MODULE
+5V+5V
POWER SUPPLY
CARRIER
CONTROL
SELECT
B
RTS/CTS DELAY SELECT
CARRIER
CONTROL
SELECT
A
LEVEL
CONVERTERS
LEVEL
CONVERTERS
P
O
R
T
A
P
O
R
T
B