TC400 Series
TCE400/TC400B
User Manual
601-00007
Rev. B
Safety Certification and Agency Approvals
Safety:
UL 60950-1:2003, First Edition
CSA C22.2 No. 60950-1-03 1st Ed. April 1, 2003
IEC 60950-1:2001 First Edition
EN 60950
AS/NZS 60950
Note: Finland, Norway and Sweden require that equipment using this
product must be located in a Restricted Access Location (RAL).
Emissions:
47 CFR Part 15, Subpart B / 47 CFR Part 15, Subpart B, Class B
EN 55022:1998 Class B / EN 55022:1998 Class B Radiated and
Conducted
EN 55024:1998 / IEC 61000
Immunity:
EN55024 ITE, EN61000
FCC Part 15:
This device complies with part 15 of FCC rules. Operation is subject to
the following two conditions: (1) This device may not cause harmful
interference, and (2) This device must accept any interference received,
including interference that may cause undesired operation.
Digium, Inc.
Page 3
Introduction to TC400 Series Documentation
sure to refer to any supplementary documents or release notes that were
shipped with your equipment. The manual is organized in the following
manner:
Chapter/
Appendix
Title
Description
Overview
Identifies the features of your card. This chapter
covers applications and uses of the TC400 Series in
the real world.
1
Card Installation
Provides instructions for installing the card in your
PC, acquiring correct drivers, and checking device
compatibility.
2
Configuration
Provides examples for configuring options.
3
4
Questions and
Answers
Explains resolutions to common problems and
frequently asked questions pertaining to card
installation and usage.
Specifications
Details card specifications.
A
B
Glossary and
Acronyms
Defines terms related to this product.
Digium, Inc.
Page 4
Symbol Definitions
Caution statements indicate a condition where damage to the unit or
its configuration could occur if operational procedures are not
followed. To reduce the risk of damage or injury, follow all steps or
procedures as instructed.
The ESD symbol indicates electrostatic sensitive devices. Observe
precautions for handling devices. Wear a properly grounded
electrostatic discharge (ESD) wrist strap while handling the device.
The Electrical Hazard Symbol indicates a possibility of electrical
shock when operating this unit in certain situations. To reduce the
risk of damage or injury, follow all steps or procedures as
instructed.
Digium, Inc.
Page 5
Important Safety Instructions
User Cautions
Power Source.
The outlet should be installed near the equipment and be easily
accessible.
Applying Power.
Use only the power cord, power supply, and/or batteries indicated in
the manual. Do not dispose of batteries in a fire. The may explode.
Check with local codes for special disposal instructions.
Installation
This card is for use only with compatible UL Listed computers that
have Installation Instructions detailing installation of card cage
accessories.
Servicing.
Do not attempt to service this card unless specifically instructed to do
so. Do not attempt to remove the card from your equipment while
power is present. Refer servicing to qualified service personnel.
Water and Moisture.
Do not spill liquids on this unit. Do not operate this equipment in a
wet environment.
Heat.
Do not operate or store this product near heat sources such as
radiators, air ducts, areas subject to direct, intense sunlight, or other
products that produce heat.
Static Electricity.
To reduce the risk of damaging the unit or your equipment, do not
attempt to open the enclosure or gain access to areas where you are
not instructed to do so. Refer servicing to qualified service personnel.
Save these instructions for future reference.
Digium, Inc.
Page 6
Chapter 1
Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11
Chapter 2
Card Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16
Unpacking the Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17
Slot Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .20
Hardware Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Software Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .23
Installing DAHDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25
Installing Asterisk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27
Chapter 3
Configuration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29
Chapter 4
Questions and Answers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30
Digium, Inc.
Page 7
Table Of Contents
Appendix A
Specifications . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32
Appendix B
Glossary and Acronyms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34
Digium, Inc.
Page 8
List of Figures
Figure 1:
Figure 2:
Figure 3:
Figure 4:
Figure 5:
Figure 6:
Sample Telco Application . . . . . . . . . . . . . . . . . . . . .12
Sample Network Application . . . . . . . . . . . . . . . . . . .13
TC400B Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .18
TCE400 Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19
Motherboard Slots . . . . . . . . . . . . . . . . . . . . . . . . . .20
Insert the Card . . . . . . . . . . . . . . . . . . . . . . . . . . . . .22
Digium, Inc.
Page 9
List of Tables
Table A-1:
Maximum Power Consumption . . . . . . . . . . . . . . . . .33
Digium, Inc.
Page 10
Chapter 1
Overview
The TC400 Series cards are a bundle of the half-length, low-profile
TC400P (PCI) or TCE400 (PCI-E) base card and the TC400M voice
processing module. The TC400 Series cards are designed to handle, in
dedicated DSP resources, the complex codec translations for highly
compressed audio as would otherwise be processed by Asterisk in
software.
Asterisk, in software and with Digium® G.729a licensing, is capable of
transforming the G.729a codec into other codecs for the purposes of call
origination or termination, bridging disparate calls, or VoIP to TDM
connectivity. These transformations in software are very expensive, in
terms of MIPS, and require a substantial amount of CPU time to
accomplish. A TC400 Series card not only relieves the CPU of this duty,
freeing it up to handle other tasks or to complete additional call
processing; but also provides Asterisk with the capability of bridging
G.723.1 compressed audio into other formats, a capability not previously
possible.
The TC400 Series cards decompress G.729a (8.0 Kbit) or G.723.1 (5.3
Kbit and 6.3 Kbit) into u-law or a-law; or, compress u-law or a-law into
G.729a (8.0 Kbit) or G.723.1 (5.3 Kbit and 6.3 Kbit). The TC400 Series
cards are rated to handle up to 120 bi-directional G.729a transformations
or 92 bi-directional G.723.1 transformations. The TC400 Series cards do
not require additional licensing fees for the use of these codecs nor do
Digium, Inc.
Page 11
Chapter 1: Overview
they require the registration process associated with Digium's software-
based G.729a codec licensing.
Features:
120 channels of bi-directional G.729a (8 Kbit) transcoding
or
92 channels of bi-directional G.723.1 (5.3 Kbit and 6.3 Kbit) transcoding
Figure 1: Sample Telco Application
Digium, Inc.
Page 12
Chapter 1: Overview
What is Asterisk®?
Asterisk is the world’s leading open source telephony engine and tool kit.
Offering flexibility unheard of in the world of proprietary
communications, Asterisk empowers developers and integrators to create
advanced communication solutions...for free. Asterisk is released as open
source under the GNU General Public License (GPL), and it is available
for download free of charge. Asterisk is the most popular open source
software available, with the Asterisk Community being the top influencer
in VoIP.
Asterisk as a Switch (PBX)
Asterisk can be configured as the core of an IP or hybrid PBX, switching
calls, managing routes, enabling features, and connecting callers with the
outside world over IP, analog (POTS), and digital (T1/E1) connections.
Asterisk runs on a wide variety of operating systems including Linux,
Mac OS X, OpenBSD, FreeBSD, and Sun Solaris. It provides all of the
features you would expect from a PBX including many advanced features
that are often associated with high end (and high cost) proprietary PBXs.
Asterisk's architecture is designed for maximum flexibility and supports
Voice over IP in many protocols, and can interoperate with almost all
standards-based telephony equipment using relatively inexpensive
hardware.
Asterisk as a Gateway
It can also be built out as the heart of a media gateway, bridging the
legacy PSTN to the expanding world of IP telephony. Asterisk’s modular
architecture allows it to convert between a wide range of communications
protocols and media codecs.
Digium, Inc.
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Chapter 1: Overview
Asterisk as a Feature/Media Server
Need an IVR? Asterisk’s got you covered. How about a conference
bridge? Yep. It’s in there. What about an automated attendant? Asterisk
does that too. How about a replacement for your aging legacy voicemail
system? Can do. Unified messaging? No problem. Need a telephony
interface for your web site? Ok.
Asterisk in the Call Center
Asterisk has been adopted by call centers around the world based on its
flexibility. Call center and contact center developers have built complete
ACD systems based on Asterisk. Asterisk has also added new life to
existing call center solutions by adding remote IP agent capabilities,
advanced skills-based routing, predictive and bulk dialing, and more.
Asterisk in the Network
Internet Telephony Service Providers (ITSPs), competitive local
exchange carriers (CLECS) and even first-tier incumbents have
discovered the power of open source communications with Asterisk.
Feature servers, hosted services clusters, voicemail systems, pre-paid
calling solutions, all based on Asterisk have helped reduce costs and
enabled flexibility.
Asterisk Everywhere
Asterisk has become the basis for thousands of communications
solutions. If you need to communicate, Asterisk is your answer. For more
Digium, Inc.
Page 15
Chapter 2
Card Installation
This chapter provides the following information:
Unpacking the Card on page 17
Shipment Inspection on page 17
Slot Compatibility on page 20
Hardware Installation on page 22
Software Installation on page 23
Note: The TC400 Series card installation instructions are written so
that they will apply to any card in the series. Examples and card
specific information are included as needed.
Digium, Inc.
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Chapter 2: Card Installation
Unpacking the Card
When you unpack your card, carefully inspect it for any damage that may
have occurred in shipment. If damage is suspected, file a claim with the
carrier and contact your reseller from which the card was purchased, or
Digium Technical Support (+1.256.428.6161). Keep the original shipping
container to use for future shipment or proof of damage during shipment.
Note: Only qualified service personnel should install the card. Users
should not attempt to perform this function.
Shipment Inspection
The following items are included in the shipment of the TC400 Series
card:
A TC400B or TCE400 card
TC400M voice processing module (installed on TC400B or TC400
card)
Caution.
Only qualified service personnel should continue with hardware
installation and configuration of the TC400 Series card. Users
should not attempt to perform these functions. This card is for
use in Listed I.T.E. (information technology equipment) only.
Digium, Inc.
Page 17
Chapter 2: Card Installation
Slot Compatibility
Check the type of card you received to be sure it is compatible with your
PCI slot. To determine which slot you have, identify it by comparing it to
those shown in the figure below.
Slot Number:
0: AGP Pro Slot
1: 64-bit 5.0 volt PCI Slot
2: 64-bit 3.3 volt PCI Slot
3: 32-bit 5.0 volt PCI Slot
4: PCI Express Slot
Slots
0
1
2
3
4
Figure 5: Motherboard Slots
Digium, Inc.
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Chapter 2: Card Installation
The TC400B is a 32-bit 33MHz card keyed for universal 3.3 volt or 5.0
volt operation and works in any PCI 2.2 (or greater) compliant slot. This
means that in the motherboard shown in Figure 5, the TC400B card will
fit into Slots 1, 2, or 3 (PCI slots) but will not fit into Slot 0 (AGP slot).
The TCE400 card is a PCI Express card. Slot 4, illustrated above, is a 1
lane (X1) PCI Express compliant slot. The TCE400 will work in any PCI
Express compliant slot, including lane lengths X1, X4, X8, and X16. This
means that in the motherboard shown in Figure 5, the TCE400 will only
fit into Slot 4. The TCE400 can not be used in Slots 0 through 3.
Digium, Inc.
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Chapter 2: Card Installation
Hardware Installation
1. Power down your computer and unplug it from its power source.
2. Attach a static strap to your wrist and open the case.
3. Remove the bracket place holder and insert the card into the PCI or
PCI Express slot. See Figure 6.
Figure 6: Insert the Card
4. Replace the cover to your computer.
Digium, Inc.
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Chapter 2: Card Installation
Software Installation
Digium hardware requires drivers and libraries that are not integrated
with the Linux kernel. Digium hardware is only supported under Linux.
Digium recommends CentOS, Debian, Red Hat, and Ubuntu distributions
of Linux. However, many other distributions are supported by Digium
Technical Support.
Digium’s software, including drivers and application software, may be
obtained from Digium’s download server at:
For an introduction to Asterisk, Digium’s telephony software, including
additional information on its configuration, setup, and features, please
refer to:
For the latest information on setting up and configuring DAHDI drivers
for your Digium hardware product, please refer to the latest release of this
manual which is available from the product-specific documentation
section at:
To install your TC400 Series card, you will need:
Linux 2.6 kernel headers
Development libraries and headers for ncurses
Development libraries and headers for zlib and openssl
Development libraries and headers for newt
GCC and standard software build tools
Digium, Inc.
Page 23
Chapter 2: Card Installation
It is recommended that you use the most recent version of the Asterisk
and DAHDI software for the best results. If you have previously installed
either of these, Digium recommends that you upgrade to the latest “-
current” version of each.
Note: If you are using the 1.4.x series of Asterisk, you will need
Asterisk 1.4.22 or newer.
Digium, Inc.
Page 24
Chapter 2: Card Installation
Installing DAHDI
1. Download the latest DAHDI drivers with tools. DAHDI is available
for download from:
dahdi-linux-complete/dahdi-linux-complete-current.
tar.gz
2. Expand the downloaded file, compile its contents, and install the
drivers and tools. Substitute the version of DAHDI for the X.X.X in
the command lines below.
# tar -zxvf dahdi-linux-complete-current.tar.gz
# cd dahdi-linux-complete-X.X.X+X.X.X
# make
# make install
3. Load DAHDI drivers into the kernel using the modprobe utility. The
appropriate driver for a TC400 Series card is wctc4xxp.
# modprobe wctc4xxp
Digium, Inc.
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Chapter 2: Card Installation
4. Confirm that the card was started successfully by running the dmesg
command.
# dmesg
The end of the output should look similar to the following:
dahdi_transcode: Loaded.
wctc4xxp: tc400b0: Attached to device at 0000:00:0a.0.
wctc4xxp: tc400b0: (G.729a / G.723.1) Transcoder support LOADED (firm ver
= 6.12)
wctc4xxp: tc400b0: Installed a Wildcard TC: Wildcard TC400P+TC400M
dahdi_transcode: Registered codec translator 'DTE Encoder' with 92
transcoders (srcs=0000000c, dsts=00000101)
dahdi_transcode: Registered codec translator 'DTE Decoder' with 92
transcoders (srcs=00000101, dsts=0000000c)
Digium, Inc.
Page 26
Chapter 2: Card Installation
Installing Asterisk
If you wish to use Asterisk with your new hardware, you can follow the
instructions below.
1. Download the latest release version of Asterisk, either 1.4.22 (or later)
or 1.6.0.1 (or later). Substitute the version of Asterisk for the X.X in
the command below. Asterisk is available for download from:
asterisk/asterisk-X.X-current.tar.gz
2. Expand the downloaded file, compile its contents, and install the
application. Substitute the version of Asterisk for the X.X and X.X.X
in the command lines below.
# tar -zxvf asterisk-X.X-current.tar.gz
# cd asterisk-X.X.X/
# ./configure
# make menuselect
# make
# make install
Digium, Inc.
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Chapter 2: Card Installation
3. If this is the first Asterisk installation on this system, you should install
the sample configuration files. To do this, run:
# make samples
Note: Running this command will overwrite, after making a backup
copy, any older Asterisk configuration files that you have in the /etc/
asterisk directory.
If your installation has failed, it may be because you are missing one
or more of the build dependencies, the kernel headers, or the
development tools. Please contact your reseller where the card was
purchased, or call Digium Technical Support (+1.256.428.6161) for
assistance.
Note: Complete instructions for installing Asterisk are available at
Digium, Inc.
Page 28
Chapter 3
Configuration
No changes to system.conf or chan_dahdi.conf are necessary to utilize
this card. The ‘mode’ module parameter may be used to specify whether
the card can be used to transcode G.729a, G.723.1, or both.
mode = mixed: This default option will enable 92 calls of G.729a or
G.723.1 (5.3 Kbit and 6.3 Kbit)
mode = g729: This option will enable 120 calls of G.729a
mode = g723: This option will enable 92 calls of G.723.1 (5.3 Kbit and
6.3 Kbit)
Testing Your Configuration:
1. Start Asterisk by typing:
# asterisk -vvvvc
2. Verify that the TC400 Series is registered with Asterisk by issuing the
following command on the Asterisk CLI.
*CLI> show transcoder
This should display the number of encoders and decoders registered
by the TC400 Series card.
Digium, Inc.
Page 29
Chapter 4
Questions and Answers
This chapter provides frequently asked questions as identified from
Digium Technical Support and possible resolutions. Multiple resources
are available to obtain more information about Asterisk and Digium
products. These resources are listed on page 31.
Q: My card can’t seem to reach its full channel count, why?
A: See next answer.
Q: Asterisk issues errors such as "rtp.c: Unable to allocate socket: Too
many open files." How can I prevent this?
A: Each call that uses a TC400 Series card for transcoding requires two
file handles. Increase the maximum number of open file descriptors
allowed on your system using the ulimit utility. First, log into a Linux
shell as the user running the asterisk process (i.e. usually root). Check the
current maximum by executing ulimit -n. Increase the maximum by
executing ulimit -n [limit](e.g. ulimit -n 32768).
Q: Does my card take 1000 interrupts per second like my other Digium
cards?
A: A TC400 Series card only takes interrupts when it is in an active
transcoding state, and will not pull interrupts when it is idling. This is
different behavior than Digium analog and digital interface cards exhibit.
Q: Does my TC400 Series card serve as a DAHDI timing device?
A: No, a TC400 Series card cannot serve as a DAHDI timing device. If
you have no other Digium cards installed which can serve as a DAHDI
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Chapter 4: Questions and Answers
timing device, you can use the dahdi_dummy kernel module to serve as
one. The dahdi_dummy kernel module can be loaded by executing
modprobe dahdi_dummy.
Where can I ask even more questions?
There are several places to inquire for more information about Digium
products:
1. Digium Technical Support (+1.256.428.6161) is available 7am-8pm
Central Time, Monday - Friday.
2. Asterisk forums (forums.digium.com).
3. Asterisk users mailing list (lists.digium.com).
4. IRC channel #asterisk on (irc.freenode.net).
Digium, Inc.
Page 31
Appendix A
Specifications
This appendix provides specifications, required environmental
conditions, and maximum power consumption for the TC400 Series
cards.
Physical.
Size:
4.69” × 2.52” × 0.63” (11.9 x 6.4 x 1.6 cm)
PCB size, does not include the PCI bracket
2.5 oz (70.9 gm)
Weight:
Interfaces.
PCI Bus (TC400B): 3.3V or 5V bus slot, half-length slot minimum
size, 33MHz minimum bus speed, compliant with PCI 2.2 or
greater.
PCI-E Bus (TCE400) - Compliant with PCI-E X1 1.0 or greater.
Environment.
Temperature: 0 to 50° C (32 to 122° F) operation
-20 to 65° C (4 to 149° F) storage
Humidity: 10 to 90% non-condensing
Digium, Inc.
Page 32
Appendix A: Specifications
Supported Codecs.
G.729a (8.0 Kbit)
G.723.1 (5.3 Kbit and 6.3 Kbit)
μ-law (u-law)
α-law (a-law)
Hardware and Software Requirements.
400 Mhz Pentium III or better
512 MB RAM
Available PCI or PCI-E Slot (as described previously)
Linux 2.6 kernel
Table A-1: Maximum Power Consumption
Model
Power
TC400B
3.3V
5V
0 Watts
4 Watts
0 Watts
12V
TCE400
3.3V
5V
0 Watts
4 Watts
5 Watts
12V
Digium, Inc.
Page 33
Appendix B
Glossary and Acronyms
a-law
Mainly used in European telephone networks for the conversion between
analog and digital signals in PCM applications. Similar to the North
American mu-law standard. Refer to G.711 on page 38 and mu-law on
page 43.
ANSI
American National Standards Institute
An organization which proposes and establishes standards for
international communications.
asynchronous
Not synchronized; not timed to an outside clock source. Transmission is
controlled by start bits at the beginning and stop bits at the end of each
character. Asynchronous communications are often found in internet
access and remote office applications.
attenuation
The dissipation of a transmitted signal’s power as it travels over a wire.
bandwidth
The capacity to carry traffic. Higher bandwidth indicates the ability to
transfer more data in a given time period.
Digium, Inc.
Page 34
Appendix B: Glossary and Acronyms
bit
The smallest element of information in a digital system. A bit can be
either a zero or a one.
bps
bits per second
A measurement of transmission speed across a data connection.
broadband
Broadband transmission shares the bandwidth of a particular medium
(copper or fiber optic) to integrate multiple signals. The channels take up
different frequencies on the cable, integrating voice, data, and video over
one line.
channel
A generic term for an individual data stream. Service providers can use
multiplexing techniques to transmit multiple channels over a common
medium.
Cat5
Category of Performance for wiring and cabling. Cat 5 cabling support
applications up to 100 MHz.
Cat5E
Category of Performance for wiring and cabling. Category 5 Enhanced
wiring supports signal rates up to 100 MHz but adheres to stricter quality
specifications.
Digium, Inc.
Page 35
Appendix B: Glossary and Acronyms
CLEC
competitive local exchange carrier
A term for telephone companies established after the
Telecommunications Act of 1996 deregulated the LECs. CLECs compete
with ILECs to offer local service. See also LEC and ILEC.
CO
central office
The CO houses local switching equipment. All local access lines in a
particular geographic area terminate at this facility (which is usually
owned and operated by an ILEC).
CPE
customer premises equipment
Terminal equipment which is connected to the telecommunications
network and which resides within the home or office of the customer. This
includes telephones, modems, terminals, routers, and television set-top
boxes.
DAHDI Digium Asterisk Hardware Device Interface
A telephony project dedicated to implementing a reasonable and
affordable computer telephony platform into the world marketplace. Also,
the collective name for the Digium-provided drivers for Digium
telephony interface products.
DS0
Digital Signal, Level 0
A voice grade channel of 64 Kbps. The worldwide standard speed for
digitizing voice conversation using PCM (Pulse Code Modulation).
Digium, Inc.
Page 36
Appendix B: Glossary and Acronyms
DS1
Digital Signal, Level 1
1.544 Mbps in North America (T1) and Japan (J1) -up to 24 voice
channels (DS0s), 2.048 Mbps in Europe (E1) - up to 32 voice channels
(DS0s). DS1/T1/E1 lines are part of the PSTN.
DS3
Digital Signal, Level 3
T3 in North America and Japan, E3 in Europe. Up to 672 voice channels
(DS0s). DS3/T3/E3 lines are not part of the PSTN
DTMF
Dual Tone Multi-Frequency
Push-button or touch tone dialing.
E1
The European equivalent of North American T1, transmits data at 2.048
Mbps, up to 32 voice channels (DS0s).
E3
The European equivalent of North American T3, transmits data at 34.368
Mbps, up to 512 voice channels (DS0s). Equivalent to 16 E1 lines.
EMI
Electromagnetic Interference
Unwanted electrical noise present on a power line
full duplex
Data transmission in two directions simultaneously.
Digium, Inc.
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Appendix B: Glossary and Acronyms
FXO
Foreign Exchange Office
Receives the ringing voltage from an FXS device. Outside lines are
connected to the FXO port on your TC400 Series card.
FXS
Foreign Exchange Station
Initiates and sends ringing voltage. Phones are connected to the FXS ports
on the TC400 Series card.
G.711
A recommendation by the Telecommunication Standardization Sector
(ITU-T) for an algorithm designed to transmit and receive mulaw PCM
voice and A-law at a digital bit rate of 64 Kbps. This algorithm is used for
digital telephone sets on digital PBX.
G.723.1
A recommendation by the Telecommunication Standardization Sector
(ITU-T) for an algorithm designed to transmit and receive audio over
telephone lines at 6.3 Kbps or 5.3 Kbps.
G.729a
A recommendation by the Telecommunication Standardization Sector
(ITU-T) for an algorithm designed to transmit and receive audio over
telephone lines at 8 Kbps.
H.323
A recommendation by the Telecommunication Standardization Sector
(ITU-T) for multimedia communications over packet-based networks.
Digium, Inc.
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Appendix B: Glossary and Acronyms
IAX
Inter-Asterisk eXchange
A VoIP protocol used by Asterisk. It is used to enable VoIP connections
between Asterisk servers, and between servers and clients that also use
the IAX protocol.
iLBC
internet Low Bitrate Codec
A free speech codec used for voice over IP. It is designed for narrow band
speech with a payload bitrate of 13.33 kbps (frame length = 30ms) and
15.2 kbps (frame length = 20 ms).
ILEC
incumbent local exchange carrier
The LECs that were the original carriers in the market prior to the entry of
competition and therefore have the dominant position in the market.
interface
A point of contact between two systems, networks, or devices.
ISO
International Standards Organization
light-emitting diode
LED
Linux
A robust, feature-packed open source operating system based on Unix
that remains freely available on the internet. It boasts dependability and
offers a wide range of compatibility with hardware and software. Asterisk
is supported exclusively on Linux.
Digium, Inc.
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Appendix B: Glossary and Acronyms
loopback
A state in which the transmit signal is reversed back as the receive signal,
typically by a far end network element.
MGCP Media Gateway Control Protocol
multiplexing
Transmitting multiple signals over a single line or channel. FDM
(frequency division multiplexing) and TDM (time division multiplexing)
are the two most common methods. FDM separates signals by dividing
the data onto different carrier frequencies, and TDM separates signals by
interleaving bits one after the other.
MUX
multiplexer
A device which transmits multiple signals over a single communications
line or channel. See multiplexing.
PBX
private branch exchange
A smaller version of a phone company’s large central switching office.
Example: Asterisk.
PCI
peripheral component interconnect
A standard bus used in most computers to connect peripheral devices.
POP
point of presence
The physical connection point between a network and a telephone
network. A POP is usually a network node serving as the equivalent of a
CO to a network service provider or an interexchange carrier.
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Appendix B: Glossary and Acronyms
POTS
plain old telephone service
Standard phone service over the public switched telephone network
(PSTN). This service provides analog bandwidth of less than 4 kHz.
PPP
point-to-point protocol
Type of communications link that connects a single device to another
single device, such as a remote terminal to a host computer.
PSTN
public switched telephone network
A communications network which uses telephones to establish
connections between two points. Also referred to as the dial network.
QoS
quality of service
A measure of telephone service, as specified by the Public Service
Commission.
RJ11
A six-pin jack typically used for connecting telephones, modems, and fax
machines in residential and business settings to PBX or the local
telephone CO.
SIP
Session Initiation Protocol
An IETF standard for setting up sessions between one or more clients. It
is currently the leading signaling protocol for Voice over IP, gradually
replacing H.323.
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Appendix B: Glossary and Acronyms
T1
A dedicated digital carrier facility which transmits up to 24 voice
channels (DS0s) and transmits data at 1.544 Mbps. Commonly used to
carry traffic to and from private business networks and ISPs.
T3
A dedicated digital carrier facility which consists of 28 T1 lines and
transmits data at 44.736 Mbps. Equivalent to 672 voice channels (DS0s).
TDM
time division multiplexer
A device that supports simultaneous transmission of multiple data streams
into a single high-speed data stream. TDM separates signals by
interleaving bits one after the other.
telco
A generic name which refers to the telephone companies throughout the
world, including RBOCs, LECs, and PTTs.
tip and ring
The standard termination on the two conductors of a telephone circuit;
named after the physical appearance of the contact areas on the jack plug.
twisted pair
Two copper wires commonly used for telephony and data
communications. The wires are wrapped loosely around each other to
minimize radio frequency interference or interference from other pairs in
the same bundle.
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Appendix B: Glossary and Acronyms
u-law
Also known as mu law, is the PCM quasi-logarithmic curve. It is the 64
Kbps standard North America voice amplitude sample used for
encoding/decoding.
V
volts
VoIP
Voice over IP
Technology used for transmitting voice traffic over a data network using
the Internet Protocol.
Digium, Inc.
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