JUNE 1999
MT120A-R2
Micro T1 CSU/DSU
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
Web site: www.blackbox.com • E-mail: info@blackbox.com
1
CE NOTICE
Trademarks Used In This Manual
AT&T is a registered trademark of American Telephone and Telegraph Company.
Any trademarks mentioned in this manual are acknowledged to be the property of
the trademark owners.
CE Notice
The CE symbol on your Micro T1 CSU/DSU indicates that it is in compliance with
the Electromagnetic Compatibility (EMC) directive and the Low Voltage Directive
(LVD) of the Union European (EU).
WARNING
This device is not intended to be connected to the public telephone
network.
2
MICRO T1 CSU/DSU
FEDERAL COMMUNICATIONS COMMISSION
AND
CANADIAN DEPARTMENT OF COMMUNICATIONS
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 the Canadian Department of
Communications.
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 le ministère des Communications du Canada.
3
NOM STATEMENT
NORMAS OFICIALES MEXICANAS (NOM)
ELECTRICAL SAFETY STATEMENT
INSTRUCCIONES DE SEGURIDAD
1. Todas las instrucciones de seguridad y operación deberán ser leídas antes de
que el aparato eléctrico sea operado.
2. Las instrucciones de seguridad y operación deberán ser guardadas para
referencia futura.
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
MICRO T1 CSU/DSU
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
FCC REQUIREMENTS
FCC REQUIREMENTS FOR
TELEPHONE-LINE EQUIPMENT
1. If you have problems with your telephone equipment after installing this
device, disconnect this device from the line to see if it is causing the
problem If it is, contact your supplier or an authorized agent.
2. The telephone company may make changes in its technical operations
and procedures. If any such changes affect the compatibility or use of
this device, the telephone company is required to give adequate notice
of the changes.
3. If the telephone company requests information on what equipment is
connected to their lines, inform them of:
a. The telephone number that this unit is connected to.
b. The ringer equivalence number.
c. The USOC jack required: RJ-11C.
d. The FCC registration number.
Items (b) and (d) can be found on the unit’s FCC label. The ringer
equivalence number (REN) is used to determine how many devices can
be connected to your telephone line. In most areas, the sum of the RENs
of all devices on any one line should not exceed five (5.0). If too many
devices are attached, they may not ring properly.
4. In the event of an equipment malfunction, all repairs should be
performed by your supplier or an authorized agent. It is the
responsibility of users requiring service to report the need for service to
the supplier or to an authorized agent.
6
MICRO T1 CSU/DSU
CERTIFICATION NOTICE FOR
EQUIPMENT USED IN CANADA
The Canadian Department of Communications label identifies certified
equipment. This certification means that the equipment meets certain
telecommunications-network protective, operation, and safety
requirements. The Department does not guarantee the equipment will
operate to the user’s satisfaction.
Before installing this equipment, users should ensure that it is permissible
to be connected to the facilities of the local telecommunications company.
The equipment must also be installed using an acceptable method of
connection. In some cases, the company’s inside wiring associated with a
single-line individual service may be extended by means of a certified
connector assembly (extension cord). The customer should be aware that
compliance with the above conditions may not prevent degradation of
service in some situations.
Repairs to certified equipment should be made by an authorized
Canadian maintenance facility—in this case, your supplier. Any repairs or
alterations made by the user to this equipment, or equipment malfunctions,
may give the telecommunications company cause to request the user to
disconnect the equipment.
Users should ensure for their own protection that the electrical ground
connections of the power utility, telephone lines, and internal metallic water
pipe system, if present, are connected together. This precaution may be
particularly important in rural areas.
CAUTION:
Users should not attempt to make such connections themselves, but
should contact the appropriate electric inspection authority, or
electrician, as appropriate.
The LOAD NUMBER (LN) assigned to each terminal device denotes the
percentage of the total load to be connected to a telephone loop which is
used by the device, to prevent overloading. The termination on a loop may
consist of any combination of devices, subject only to the requirement that
the total of the load numbers of all the devices does not exceed 100.
7
CONTENTS
Contents
Chapter Page
1. Specifications ........................................................................................................8
2. Introduction ..........................................................................................................9
2.1 Description ..................................................................................................9
2.2 Features ........................................................................................................9
2.3 Supported Applications ..............................................................................9
2.3.1 As an Interface Between the Telco and CPE ................................10
2.3.2 As a High-Speed Short-Range Modem ..........................................10
3. Configuration ......................................................................................................11
4. Installation............................................................................................................18
4.1 DTE Interface Connection........................................................................18
4.2 Network Interface Connection ................................................................18
4.3 Power Connection ....................................................................................18
5. Operation ............................................................................................................19
5.1 LED Descriptions ......................................................................................19
5.2 Central Office Loops ................................................................................20
Appendix A: Cable Recommendations ..................................................................22
Appendix B: Pin Assignments ..................................................................................23
Appendix C: Power-Supply Interface ......................................................................24
8
MICRO T1 CSU/DSU
1. Specifications
WAN Speed — 1.544 Mbps
WAN Connection — RJ-48C
Nominal Impedance — 100 ohms
DTE Interface — Integral V.35, M/34 male
Line Coding — AMI/B8ZS
Line Framing — D4/ESF
Receive LBO — Automatic
Transmit LBO — Selectable: 0, 7.5, 15, or 22.5 dB
Clock Options — Internal, external, and network clock
Diagnostics — Responds to CO-initiated D4 loop-up and loop-
down codes, ESF line loop and payload loop
FDL messages, universal loopback de-activate
message
Standards — AT&T
®
TR62411, ANSI T1.403, TR54016
Power Supply — 120 VAC, 60 Hz to 5 VDC 300-mA wallmount
transformer (for DTE power options, see
Appendix C)
Size — 0.8"H x 2.1"W x 4.5"D (2 x 5.3 x 11.4 cm)
9
CHAPTER 2: Introduction
2. Introduction
2.1 Description
The Micro T1 CSU/DSU supports a single T1 or Fractional T1 connection at data
rates of 1.544 Mbps (unstructured), n × 64, and n × 56. Plug the Micro T1
CSU/DSU directly into the WAN port of a switch, router, or multiplexor.
The Micro T1 CSU/DSU is easily configurable using two PC-board-mounted DIP
switches. Use the DIP switches to set D4 or ESF framing modes, AMI or B8ZS line
coding, clocking modes, T1 starting channel, Line Build Out, and data rate.
Connecting directly to the V.35 interface, the ultra-compact Micro T1 CSU/DSU
attaches without using additional cables. Twisted-pair line connections are made
through a modular RJ-48 female jack on the rear of the unit.
Seven easy-to-read LED indicators monitor data, network, and test signals.
2.2 Features
• Operates over 4-wire T1 (DS1) circuits.
• Supports unstructured rates at 1.544 Mbps.
• Supports common framed n × 56/64 rates up to 1.536 mbps.
• Seven easy-to-read LEDs monitor data and diagnostics.
• Internal or external network clocking.
• Also works as a high-speed point-to-point modem.
• Compact size; plugs directly into a router, switch, or other DTE.
2.3 Supported Applications
The Micro T1 CSU/DSU supplies the interface between the telephone-company
and customer-premises equipment (such as a router). The Micro T1 CSU/DSU
can also be used as a high-speed short-haul modem for campus applications.
10
MICRO T1 CSU/DSU
2.3.1 A
SAN
I
NTERFACEBETWEEN THETELCO AND
CPE
The Micro T1 CSU/DSU provides the interface between the telephone company
and customer equipment (such as a router or switch).
2.3.2 ASAH
IGH-SPEEDSHORT-RANGEMODEM
The Micro T1 CSU/DSU can also be installed in high-speed campus applications.
In this application, a pair of Micro T1 CSU/DSUs operate as short-range modems.
Bridge/Router
Bridge/Router
Micro T1 CSU/DSU
1.544 Mbps
or nx56/64
1.544 Mbps
or nx56/64
Micro T1 CSU/DSU
LAN
LAN
Micro T1 CSU/DSU
LAN
Router
T1 Network
11
CHAPTER 3: Configuration
3. Configuration
Before operating the Micro T1 CSU/DSU, you must configure it to match both the
DTE and Network Interface parameters using the DIP-switch packages on the
bottom of the printed circuit board (see Figure 3-1) or via software using the
RS-232 control port.
Figure 3-1. Bottom view, showing the DIP switches.
Figure 3-2 shows the orientation of the DIP switches with respect to ON/OFF
positions.
Figure 3-2. Closeup of DIP switches.
DIP Switches SW2 and SW1
ON
OFF
SW1SW2
12
MICRO T1 CSU/DSU
DIP S
WITCHES
SW1-SW8
The configuration switches on the DIP switches allow you to specify data rates, line
framing and coding, DS0 rate, clock mode, starting channel, and Line Build-Out
(LBO). Factory-default settings of all switches are shown in the table below.
Table 3-1. Switch Setting Summary Table.
Position Function Factory Default Option
SW1-1 Starting Channel Off
SW1-2 Starting Channel Off Starting from
SW1-3 Starting Channel Off Channel 1
SW2-7 Starting Channel Off
SW2-8 Starting Channel Off
SW1-4 Data Rate Off
SW1-5 Data Rate Off
SW1-6 Data Rate Off
SW1-7 Data Rate On 1.536 Mbps
SW1-8 Data Rate On (DTE Rate)
SW2-1 Clock Off Network
SW2-2 DS0 Rate/Clock* On 64 kbps
SW2-3 Frame Off ESF
SW2-4 Line Code Off B8ZS
SW2-5 Line Build Out Off
SW2-6 Line Build Out Off 0 dB
*In unframed mode, SW2-2 is used with SW2-1 to determine the clocking mode.
In framed modes (ESF or D4) only network and internal clocking are available. In
unframed mode, where the DTE data rate is 1.544 Mbps, a third clocking option is
available—external clocking, in which the CSU derives its transmit timing source
from the DTE (see Appendix D for external timing pin data).
Table 3-2. Clocking Mode.
Function SW2-1 SW2-2 Clocking Mode
Framed Off Don’t Care Network
Mode On Don’t Care Network
(ESF/D4)
Unframed Off Don’t Care Network
Mode On Off Internal
On On External
13
CHAPTER 3: Configuration
S
WITCHES
SW1-8, SW1-7, SW1-6, SW1-5,
AND
SW1-4
These switches set the DTE data rate. Each setting represents an n × 56/n × 64
setting. Table 3-3 shows the switch settings and the achieved DTE data rate.
Table 3-3. DTE Data Rate.
SW1-4 SW1-5 SW1-6 SW1-7 SW1-8 DTE Data Rate
Off Off Off Off Off 1544 kbps (unframed)
On Off Off Off Off 56/64 kbps (n=1)
Off On Off Off Off 112/128 kbps (n=2)
On On Off Off Off 168/192 kbps (n=3)
Off Off On Off Off 224/256 kbps (n=4)
On Off On Off Off 280/320 kbps (n=5)
Off On On Off Off 336/384 kbps (n=6)
On On On Off Off 392/448 kbps (n=7)
Off Off Off On Off 448/512 kbps (n=8)
On Off Off On Off 504/576 kbps (n=9)
Off On Off On Off 560/640 kbps (n=10)
On On Off On Off 616/704 kbps (n=11)
Off Off On On Off 672/768 kbps (n=12)
On Off On On Off 728/832 kbps (n=13)
Off On On On Off 784/896 kbps (n=14)
On On On On Off 840/960 kbps (n=15)
Off Off Off Off On 896/1024 kbps (n=16)
On Off Off Off On 952/1088 kbps (n=17)
Off On Off Off On 1008/1152 kbps (n=18)
On On Off Off On 1064/1216 kbps (n=19)
Off Off On Off On 1120/1280 kbps (n=20)
On Off On Off On 1176/1344 kbps (n=21)
Off On On Off On 1232/1408 kbps (n=22)
On On On Off On 1288/1472 kbps (n=23)
Off Off Off On On 1344/1536 kbps (n=24)
14
MICRO T1 CSU/DSU
S
WITCHES
SW1-1, SW1-2, SW1-3, SW2-7, SW2-8
These switches set the starting channel, which is the first channel that carries valid
data. You can set this channel to any value between 1 and 24. If the starting
channel is other than 1, then the maximum possible bandwidth will be less than
1536 kbps. For example, if the starting channel is set to be 12, then the maximum
bandwidth is limited to 13 × 64 kbps (channels 12–24), or 832 kbps. Keep this in
mind when setting the starting channel. The Micro T1 CSU/DSU will flash the
ERR indicator LED if the switch setting is invalid. Refer to Section 5.1 for a more
detailed explanation of the ERR LED function.
Table 3-4. T1 Starting Channel.
SW1-1 SW1-2 SW1-3 SW2-7 SW2-8 T1 Starting Channel
(maximum value of n)
Off Off Off Off Off 1 (24)
Off Off Off On Off 2 (23)
Off Off Off Off On 3 (22)
Off Off Off On On 4 (21)
On Off Off Off Off 5 (20)
On Off Off On Off 6 (19)
On Off Off Off On 7 (18)
On Off Off On On 8 (17)
Off On Off Off Off 9 (16)
Off On Off On Off 10 (15)
Off On Off Off On 11 (14)
Off On Off On On 12 (13)
On On Off Off Off 13 (12)
On On Off On Off 14 (11)
On On Off Off On 15 (10)
On On Off On On 16 (9)
Off Off On Off Off 17 (8)
Off Off On On Off 18 (7)
Off Off On Off On 19 (6)
Off Off On On On 20 (5)
On Off On Off Off 21 (4)
On Off On On Off 22 (3)
On Off On Off On 23 (2)
On Off On On On 24 (1)
15
CHAPTER 3: Configuration
S
WITCHES
SW2-6
AND
SW2-5 L
INEBUILDOUT
These switches are used to set the line build out (LBO). The LBO controls the
pulse shape and attenuation of the signal sent to the network. The amount of LBO
depends on the distance to the nearest repeater. The telephone company
providing the T1 service will advise you of the required LBO setting.
Table 3-5. LBO Setting.
SW2-5 SW2-6 LBO
Off Off 0 dB, 0–133 ft.
On Off -7.5 dB
Off On -15.0 dB
On On -22.5 dB
S
WITCH
SW2-4 L
INECODING
This switch is used to set the line code. Two coding options are available through
the DIP switches: B8ZS and AMI. The line code refers to the way that the signal—
the sequence of ones and zeros sent to the network—is encoded. AMI reverses the
polarity of consecutive pulses. B8ZS is identical to AMI, except that, under certain
circumstances, the alternate polarity rule is deliberately violated.
AMI: This stands for “Alternate Mark Inversion.” The CSU/DSU transmits data as a
sequence of ones and zeros. Ones are usually sent as pulses, and zeros as spaces
(no pulse). In order to maximize transmission range, every pulse is of the opposite
polarity of the preceding pulse. AMI does nothing else. Maintaining network
integrity requires a minimum pulse density (ones density) of the signal being
transmitted on the network. AMI does not inherently provide for this feature.
Thus, if a long sequence of zeros happen to be sent, the network may suffer. To
meet this requirement using AMI requires one of two methods: Reduce the rate of
each time slot (DS0) to 56 kbps, so that the last bit can be used to guarantee the
minimum ones density. Or, make sure that the DTE sends data in such a way that
ones density is always maintained. For this reason, you may prefer B8ZS over AMI.
B8ZS: This stands for “Bipolar 8 Zero Substitution.” This line code ensures
minimum ones density. Long sequences of zeros are specially encoded. This line
code allows any data pattern to be transmitted without causing ones density
problems. Thus, it allows the use of 64-kbps timeslots.
Table 3-6. Line Codes.
SW2-4 Line Code
Off B8ZS
On AMI
16
MICRO T1 CSU/DSU
S
WITCH
SW2-3 L
INEFRAMING
This switch is used to set the frame. There are three framing modes available in the
Micro T1 CSU/DSU: ESF, D4, and Unframed. When SW1-4 through SW1-8 are
turned off, the unit is set to unframed operation, and SW2-3 is ignored. Otherwise,
SW2-3 is used to set the frame to either ESF or D4.
Table 3-7. SW2-3 Line Framing.
SW2-3 Frame
Off ESF
On D4
L
INE-FRAMINGOPTIONS
D4/Superframe: The D4 framing format, as specified in AT&T TR62411, is the
standard in which twelve frames make up a superframe. All signaling and
synchronization is done in-band.
Extended Superframe: Extended Superframe, as specified in AT&T TR 54016,
consists of 24 T1 frames. The framing bits are now used for framing CRC and the
Facility Data Link (FDL). The FDL allows maintenance messages and information
to be passed between the CSU/DSU and the central office.
S
WITCH
SW2-2 DS0 C
HANNEL
R
ATE
This switch is used to set the DS0 rate in framed modes; in unframed mode, this
switch is used with SW2-1 to set the clocking mode.
Table 3-8. DS0 Channel Rate.
SW2-2 DS0 Rate
Off 56 kbps
On 64 kbps
17
CHAPTER 3: Configuration
S
WITCH
SW2-1 C
LOCKMODE
This switch is used to select the timing source for transmitting data to the network.
External clocking is available only in unframed mode (DTE data rate of 1.544
Mbps).
Table 3-9. Clocking and Framing Modes.
Function SW2-1 SW2-2 Clocking Mode
Framed Mode Off Don’t Care Network
(ESF/D4) On Don’t Care Internal
Unframed Mode Off Don’t Care Network
On Off Internal
On On External
NOTE
When using the Micro T1 CSU/DSU to terminate the telephone
company’s T1 service, the Micro T1 CSU/DSU must be set to network
clock. When using the CSU/DSU as a high-speed short-range modem,
one unit of the link must be configured for Internal Clock mode, and
the unit on the opposite end must be configured for Network Clock
mode.
18
MICRO T1 CSU/DSU
4. Installation
The Micro T1 CSU/DSU is equipped with a DTE, network, and power interface.
This section briefly describes connection to each.
4.1 DTE Interface Connection
The DTE interface is a V.35 DCE presented as an M/34 male connector. This
interface is designed to plug directly into a DTE interface. (See Appendix B for
V.35 interface pin assignments.)
4.2 Network Interface Connection
The Network Line Interface is an eight-position keyed modular RJ-48C jack. This
interface will need to be configured to match the line parameters (that is, framing
and line coding) supplied by the Central Office.
NOTE
If the Micro T1 CSU/DSU is being used for private short-range modem
applications, the twisted-pair cable connected to its port will need to be
a crossover cable. See Appendix B for interface pin assignments.
4.3 Power Connection
The Micro T1 CSU/DSU is powered via a supplied external transformer, which
connects to the barrel jack on the rear of the Micro T1 CSU/DSU. The Micro T1
CSU/DSU can also be powered via the DTE interface when supplied with 5 VDC @
300 mA to Pin KK. See Appendix C for more information.
19
CHAPTER 5: Operation
5. Operation
Once the Micro T1 CSU/DSU is installed and configured properly, it is ready to
place into operation.
5.1 LED Descriptions
The Micro T1 CSU/DSU is equipped with seven LEDs that monitor the status of
communication. Figure 5-1 shows the location of the LEDs on the Micro T1
CSU/DSU.
ERR Error. Flashes to indicate errors.
Invalid Switch Configuration: You might request more bandwidth than
is possible. For instance, if you set the starting channel to 12, and you
select a number of timeslots exceeding 13, the unit will not be able to
satisfy your request. In that case, the ERR LED will flash once a second
(
1
⁄2 second on, 1⁄2 second off). When the unit detects an invalid setting, it
will ignore the setting and default to a full T1 (bandwidth=24 channels,
starting channel=1). This will continue until you set the switches to a
valid setting. The invalid switch configuration condition overrides
other error conditions.
20
MICRO T1 CSU/DSU
Errored Second: In ESF or SF framing, if the unit detects a frame
error, the ERR LED will flash briefly once a second.
Framing Mismatch: The ERR LED flashes briefly once a second when
framing modes are mismatched.
Loss of Signal: When there is no signal at the network interface, the
ERR LED will flash briefly once a second.
TXD Transmit Data. Lit green to indicate data flow to the Micro T1
CSU/DSU from the DTE.
RXD Receive Data. Lit green to indicate data flow from the Micro T1
CSU/DSU to DTE.
LOS Loss of Sync. Lit red to indicate a network Loss of Frame or Loss of
Signal condition.
ALM Alarm. Lit red to indicate that one of several alarm conditions exists.
These conditions may be local alarms or remote alarm conditions.
Alarms may occur due to Loss of Synchronization, Loss of Frame, AIS
(Blue Alarm), or Yellow Alarm.
ERR Error. Lit red to indicate the detection of an Errored Second (ES). An
Errored Second is any second in which a SuperFrame or Extended
Superframe error event has occurred.
TST Test/Loop. Lit yellow to indicate that the unit is in test mode. The unit
may be in any one of the following modes: D4 Line Loop (CO
initiated), ESF Line Loop (CO Initiated), ESF Payload Loop (CO
Initiated).
PWR Power. Lit green to indicate that the unit is receiving power.
21
CHAPTER 5: Operation
5.2 Central Office Loops
The Micro T1 CSU/DSU also responds to central-office-initiated loop commands.
When in D4 framing mode, the Micro T1 CSU/DSU will implement the “loop up”
command when it recognizes the pattern “10000” in the data stream for a
minimum of 5 seconds. The “loop down” command is implemented by the pattern
“100” in the data stream for a minimum of 5 seconds.
When operating in ESF framing mode, loopback commands are issued via the
Facility Data Link (FDL). The line loop message will cause a loopback before data
enters the framer portion of the CSU. The payload loop message will cause the
Micro T1 CSU/DSU to loop data after the framer portion of the CSU.
The Micro T1 CSU/DSU will respond to Universal Loopback Deactivate to clear all
central-office loops.
22
MICRO T1 CSU/DSU
Appendix A. Cable
Recommendations
The Micro T1 CSU/DSU operates at frequencies of 20 kHz or less and has been
performance tested using twisted-pair cable with the following characteristics:
Wire Gauge Capacitance Resistance
19 AWG 83 nf/mi. or 15.72 pf/ft. 0.0163 ohms/ft.
22 AWG 83 nf/mi. or 15.72 pf/ft. 0.0326 ohms/ft.
24 AWG 83 nf/mi. or 15.72 pf/ft. 0.05165 ohms/ft.
For optimum performance:
• Always use twisted-pair wire; this is not an option.
• Use twisted-pair wire with a capacitance of 20 pF/ft. or less.
• Avoid twisted-pair wire thinner than 26 AWG (avoid higher AWG numbers
than 26).
• Use of twisted pair with a resistance greater than the specifications above may
cause a reduction in maximum distance obtainable. Functionality should not
be affected.
• Many environmental factors can affect the maximum distances obtainable at a
particular site. Use the data-rate/distance table above as a general guideline
only.
23
Appendix B. Pin Assignments
RJ-48C T1 (DS0) Network Interface
(RJ-48 female modular jack)
Pin # Signal
1 RX Data (TIP)
2 RX Data (RING)
4 TX Data (TIP)
5 TX Data (RING)
M/34 Connector Terminal Interface
Pin # Signal
A GND (Earth Ground/Shield)
B SGND (Signal Ground)
C RTS
D CTS
E DSR
FCD
H DTR
PTD
RRD
S TD/
T RD/
U XTC (Transmit Clock +, DTE Source)
V RC (DCE Source)
W XTC/ (Transmit Clock -, DTE Source)
X RC/
YTC
AA TC/
KK Aux. Power Input (+5 VDC @ 300 mA)
APPENDIX B: Pin Assignments
24
MICRO T1 CSU/DSU
Appendix C. Power-Supply
Interface
Main 5 VDC power jack (J1)
Center Pin: 5 VDC @300 mA
Outer Barrel: Ground
Auxiliary Power: Supplied to Pin KK on V.35 connector
Jumper Position for Power via DC Power Jack (Default).
Jumper Position for Power via Pin KK.
1000 Park Drive • Lawrence, PA 15055-1018 • 724-746-5500 • Fax 724-746-0746
© Copyright 1999. Black Box Corporation. All rights reserved.
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