Black Box ME800A Plus User manual

AUGUST 2000
ME800A Plus
ME800AE Plus
Short-Haul Modem B Plus
(SHM-B Plus Async)
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]
TD
RD
NORMAL
LOOPBACK

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SHM-B PLUS ASYNC
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 J 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 classe A prescrites dans le Règlement sur le
brouillage radioélectrique publié par Industrie Canada.

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SHM-B PLUS ASYNC
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.

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SHM-B PLUS ASYNC
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.
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.

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SHM-B PLUS ASYNC
TRADEMARKS USED IN THIS MANUAL
Any trademarks mentioned in this manual are
acknowledged to be the property of the trademark
owners.

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SHM-B PLUS ASYNC
1. Specifications
Transmission —
Data Rate (bps) AWG (mm)
24 (0.5) 26 (0.4)
Distance in miles
115,200 0.8 0.7
57,600 1.2 0.8
38,400 1.3 0.9
19,200 1.5 1.2
9600 2 1.5
4800 2.6 2
2400 4 3
1200 4.8 4
NOTE:The above specifications are valid for 24- or 26-AWG unshielded
twisted-pair telephone cable insulated by polyethylene with a
mutual capacitance of 0.083 pf/mile. Shielded twisted-pair cable
will reduce the distance to one-third of the table value, due to the
additional capacitance contributed by the cable’s shielding. Actual
distances may vary depending on your specific operating
equipment and the cable you use.
Protocol — Asynchronous
Operation — 4-wire, full duplex, point-to-point
Line Interface — Balanced current loop; Receive lines
are protected through optical isolators rated at 1500
volts

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SHM-B PLUS ASYNC
Equipment Interface — EIA-232/CCITT V.24 interface
with a hardware handshake (selected through use of an
external switch). Data Carrier Detect (DCD) true (high)
indicates operating short-haul modem at the remote
end of the loop. Interface is switch-selectable for
DTE/DCE configuration (pins 2 and 3 reversed, pins 4
and 5 reversed with pin 8, pin 6 reversed with pin 20)
Connectors — (1) DB25 female, (1) 4-screw terminal
block, (1) RJ-11 (6 positions, 6 contacts), (1) 4-position
mini-DIN jack
Diagnostics — Loopbacks provided by a front-panel
switch: Analog loopback on a 4-wire loop and digital
loopback on equipment interface (EIA-232)
Status Indication — Two bi-color LEDs indicate the
status of the transmitter and receiver. A green light
indicates a “low” logic level (-3 to -15V) on the EIA-232
interface; a red light indicates a “high” logic level (+3 to
+15V).
Operating Temperature — 32 to 112°F (0 to 50°C)
Humidity — 90%maximum, noncondensing

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SHM-B PLUS ASYNC
Enclosure — High-impact plastic
Power — Power is supplied by a wall-mounted power
transformer. No more than 16 Vrms is present in unit.
Primary: 115 VAC ±10%, 60 Hz, 5 watts (12 watts max.);
Primary: 230 VAC ±10%, 50/60 Hz; Secondary: 17 VAC,
700 mA
Size — 1.3"H x 4"W x 4.2"D (3.3 x 10.7 x 11.3 cm)
Weight —1.4 lb. (0.6 kg), standalone, including
transformer

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SHM-B PLUS ASYNC
2. Introduction
The Short-Haul Modem Model B Async Plus (SHM-B
Async) is an asynchronous full-duplex 4-wire line
driver/receiver which allows two EIA-232 devices to
communicate at distances of up to 4 miles and at data
speeds of up to 115.2 kbps. In addition to the
transmitter and receiver circuits, the SHM-B Async Plus
includes EIA-232 control line interfaces, status monitor
LEDs, and a loopback switch. The SHM-B is available as
a standalone version (ME800A-Plus).
The SHM-B is designed to operate over a 4-wire metallic
circuit. Optimum performance is obtained with twisted-
pair cable (see specifications). Most types of twisted-pair
cable may be used, often with little or no performance
degradation.
The SHM-B Async is designed for maximum operator
safety. There are no voltages greater than 12 VDC or 16
VAC present on the circuit board of the unit. The
Receive lines are protected from potential ground
differences through optical isolators rated at 1500 volts.

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SHM-B PLUS ASYNC
3. Installation
Installation involves three basic steps: four-wire
connections; EIA-232 connection; switch settings.
3.1 Four-Wire Connections
Connect pairs of modems using the terminal block or
RJ-11 connectors provided. Figure 1 shows the location
of the terminal block and the RJ-11 jack.
a) TERMINAL BLOCK:
Refer to Figure 2 to make the proper connections
between two SHM-B units using the terminal block.
NOTE: Transmit + (TX+) on one modem is wired
to Receive + (RX+) on the other modem; Transmit -
(TX-) is wired to Receive - (RX-).
1. Strip each of the four wires about 1⁄8".
2. Loosen the screw terminals in the terminal block.
Insert the wires into the terminal strip; tighten the
screw terminals.

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SHM-B PLUS ASYNC
Figure 1. Bottom View.
Figure 2. Wiring Diagram—Terminal Block.
TX-
TX+
RX-
RX+
RX+
RX-
TX+
TX-
S3
RTS/DTR
CONTROL
RJ11
CONNECTOR
TERMINAL
BLOCK
S1
DTE/DCE
DTE
DCE
EN
DIS
J1
RS-232
CONNECTOR
POWER
CONNECTOR
S2
LOOPBACK
RD LED
TD LED
TX+
TX-
RX+
RX-
SHM #1 SHM #2

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SHM-B PLUS ASYNC
b) RJ-11 JACK:
1. Connect pairs of modems using a crossover RJ-11
cable (refer to Figure 3). A crossover cable has the
RJ-11 tabs on the same side of the cable.
2. Insert the RJ-11 cable into both local and remote
modem’s jack.
Figure 3. RJ-11 Jack.
CROSSOVER CABLE
1
TX+ 2
TX- 3
RX- 4
RX+ 5
6
6
5 RX+
4 RX-
3 TX-
2 TX+
1
Wiring Diagram
SHM #2SHM #1

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SHM-B PLUS ASYNC
3.2 EIA-232 Connection
Connect the SHM-B to your computer or terminal with a
standard EIA-232 cable and DB25 connectors. Refer to
your equipment’s installation manual if you need
information on the exact EIA-232 signals required for
your equipment. Often, it is best to use only the
Transmit Data (TD), Receive Data (RD), and ground
lines if your equipment does not require the use of the
control signals Request To Send (RTS), Clear To Send
(CTS), Data Set Ready (DSR), etc. The SHM-B
generates levels for the control signals if you need to use
them. The table shows the pin connections at the SHM-
B.
Table 1. EIA-232 Pin Connections on SHM-B
Pin Number Signal Name
1 Protective Ground
2 Transmit Data/Receive Data (TD/RD)*
3 Receive Data/Transmit Data (RD/TD)*
4 Request to Send (RTS/DCD)*
5 Clear to Send (CTS/RTS)*
6 Data Set Ready (DSR/DTR)*
7 Signal Ground
8 Data Carrier Detect (DCD/RTS)*
20 Data Terminal Ready (DTR/DSR)*
*TD and RD, RTS and DCD, DSR and DTR can be reversed using the DTE/DCE switch
S1 on the circuit board. See Section 3.3 for details.

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SHM-B PLUS ASYNC
3.3 Switch Settings
DTE/DCE S WITCH
Refer to Figure 1 in this chapter. Switch S1 is used to
reverse the TD, RD, and hardware flow control lines on
the EIA-232 interface. This eliminates the need to swap
these signals in your EIA-232 cables. If you connect the
SHM-B to your equipment using a “straight-through” or
“2:2” cable, then S1 must be set to the opposite of your
device’s configuration. For example, if your device is
configured as DTE, select DCE on S1. If you use a null
modem, “2:3”, or “3:2” cable to connect the SHM-B to
your equipment, then the setting for S1 will be identical
to your equipment’s setting. Refer to your equipment’s
manual for information concerning its DTE/DCE
setting. Table 2 gives the EIA-232 pinning of the SHM-B
with the DTE/DCE switch in the DCE position.

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SHM-B PLUS ASYNC
Table 2. Pinning with DTE/DCE switch in the DCE position.
PIN NUMBER SIGNAL NAME DIRECTION
1 Protective Ground —————
2 Transmitted Data TD* To DCE
3 Received Data RD* From DCE
4 Request to Send (RTS)* To DCE
5 Clear to Send (CTS)* From DCE
6 Data Set Ready (DSR)* From DCE
7 Signal Ground —————
8 Data Carrier Detect (DCD)* From DCE
20 Data Terminal Ready (DTR)* To DCE
*Pins 2 and 3 (TD and RD), and hardware flow control can be reversed using the
DTE/DCE switch, S1 on the circuit board.
NOTE
Configure each SHM-B independently. Your local and
remote modems won’t necessarily be configured the same.

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SHM-B PLUS ASYNC
3.4 Flow Control Switch
The SHM-B uses a clever, yet simple way to allow this
unit to work with a broad line of equipment.
S TANDARD EIA-232C H ANDSHAKING (RTS/DTR C ONTROL
S WITCH S3 IN EN P OSITION )
The individual SHM-B modems force their own DTR,
RTS, CTS, and DSR control lines HIGH (>+3V) when:
• The twisted-pair wires are installed correctly.
• Power is applied to the modems.
• No computer devices are attached to the modems.
This forces DCD HIGH on the remote modem; thus, the
remote modem knows to expect data. In this state, “all
systems are go.” The only way this state changes is if your
equipment overrides this condition. For example, if your
equipment drops DTR to a NEGATIVE signal, your
equipment’s DTR being low will override the SHM-B’s
DTR, and DCD on the remote modem will go LOW.
Because DTR, DSR, RTS, and CTS are tied together
internally, dropping any one of these four signals to a

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SHM-B PLUS ASYNC
negative state will also drop DCD on the remote side to a
negative state. DCD will also go LOW if the remote
SHM-B is powered down, or if the twisted-pair wire is
broken.
X-ON/X-OFF M ODE
(RTS/DTR C ONTROL S
WITCH [S3] IN DIS P OSITION )
If X-ON/X-OFF characters are used for handshaking
control, rather than hardware logic levels, move the
RTS/DTR control switch to the DIS position.
Typically, units that use software X-ON/X-OFF flow
control do not want RTS to affect DCD on the remote
SHM-B. Moving the switch to the DIS position disables
the RTS/DCD relationship. The only thing that will
force DCD low with the switch in the DIS position is the
absence of power on the remote SHM-B or a broken
twisted-pair wire.

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SHM-B PLUS ASYNC
4. Operation
After completing the wiring and configuration
procedure, connect the SHM-B to your equipment, then
plug the wall transformer into its power source and into
the SHM-B. Check the SHM-B operation at both ends of
the loop by pressing the LOOPBACK switch, S2.
Figure 4. Activating the LOOPBACK switch.
TD TX+
TX-
RD RX+
RX-
(RS-232)
SHM #1 in NORMAL mode.
RD
RX+
RX-
TD
TX+
TX-
(RS-232)
SHM #2 in NORMAL mode.
TD TX+
TX-
RD RX+
(RS-232)
SHM #1 in LOOPBACK mode.
RD
RX+
RX-
TD
TX+
TX-
(RS-232)
SHM #2 in NORMAL mode.
RX-

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SHM-B PLUS ASYNC
When in loopback mode, the switch button indicator
will appear white. If a CRT terminal is connected to the
SHM-B, typing characters on the keyboard should result
in the same characters appearing on the CRT screen. If
no characters appear, check your EIA-232 connections
and the setting of S1. See Figure 4 for an illustration of
the loopback mode.
The TD and RD LEDs on the front panel of your SHM-B
indicate the status of the SHM-B transmitter and
receiver, respectively. Green indicates a LOW EIA-232
level and red indicates a HIGH EIA-232 level. The LEDs
will modulate as data is transmitted and received by the
SHM-B. Remember that these LEDs are monitoring the
actual received and transmitted signals, not the TD and
RD lines of the EIA-232 interface.
When the loopback test is completed, press the
LOOPBACK switch again to return the SHM-B to
normal mode. The switch button indicator should now
be black. Data transmission between the two modems
will now be possible.
If you experience problems communicating between the
two SHM-Bs, use Chapter 5 to help diagnose the
problem.

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SHM-B PLUS ASYNC
5. Troubleshooting Guide
The following information will help you troubleshoot
your installation if problems develop. If your particular
situation isn’t listed here, call Technical Support for
assistance. Have ready a description of the problem with
your installation, your DTE equipment make and
models, your equipment’s DTE/DCE configuration and
flow control type (hardware or software), your EIA-232
cable pinouts, and what (if anything) you have already
done to correct the situation.
SYMPTOM: LEDs do not light when power transformer
is plugged into a wall outlet.
1. Is the power connection loose? Try moving or
nudging the wall transformer.
2. If the LEDs still do not light, the SHM-B may be
defective.
SYMPTOM: No data transfer in one or both directions
(to, from, or to-and-from the SHM-B).
1. Monitor the TD LED on the sending-end modem
while sending data. The light should flash red/green.