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MCLD - Modifying Calling Line Disconnect. The parameter on the Lucent 5ESS switch that determines if CPC is active. Should be set to “Yes” if CPC is required. See CPC.
National ISDN (USA & Canada) - The U.S. “standardized” multi-platform ISDN protocol. The first version is National ISDN-1. As of mid-1996, National ISDN-2 has been implemented in some areas and is fully backward compatible with National ISDN-1.
NCTE – Network Channel Terminating Equipment. NCTE is a general term that can be applied to a CSU or NT1 or other equipment terminating a digital line at the customer’s premises. In many countries, the NCTE is provided by the Telco. The U.S. is not one of those countries.
Network Channel Terminating Equipment - See NCTE.
Network Termination - See NT.
NIU – Network Interface Unit, a line-powered, telephone company-owned interface card that provides a remote-controlled loopback function, some error monitoring, and signal level conditioning. Sometimes called an "NI" or "Smart Jack," it is typically a box in a locked cabinet on the wall with some lights that has at least one RJ45 jack and a cable going to either the RJ21x block or another demarc. The NIU converts the incoming 2-pair line to an RJ45 T1 or PRI line. A CSU/DSU is required between it and your equipment to handle the level conversion and provide your own loopback capability. The NIU and the cable going to it are the phone company’s property and their maintenance responsibility. Also a nice little college in Illinois.
Northern Telecom - The Canadian company which was once the manufacturing arm of Bell Canada (and formerly called Northern Electric back then). Now called Nortel Networks. See Nortel.
NT - Network Termination. The electrical and protocol specifications for the user end of an ISDN line. See also LT.
NT-1 - An alternative expression for NT1. See NT1.
NT1 (Network Termination Type 1) - The termination at the customer premises of an ISDN BRI circuit. The NT1 performs the role of line termination of the “U” interface and codes/ decodes from the line’s 2B1Q coding scheme. The customer end of the NT1 interfaces using the “S” or “T” interface. The NT1 is frequently part of the “Terminal Adapter” and is built-in to Zephyr Xstream, Zephyr, ZephyrExpress, Telos TWO, and Telos TWOx12 systems sold in the U.S. & Canada. See also NCTE.
NTBA - Network Termination Basic Access. The term used for NT1 in some countries. See NT1. See also NCTE.
OOS – Out of Service. An alarm light or condition on a T1 or trunk.
Packet Switching - Packet-switched networks are more commonly associated with Computers, Local Area Networks, and the Internet. In a packet-switched network, the raw stream of data is broken into individual pieces called packets. Each packet is routed through the data network individually. This is somewhat analogous to taking the pages of a book and sending each page as a letter through the postal system. The page numbers would allow reassembly of the book no matter what order the pages were received at the far end. The end-user does not know or care that the packets may travel a variety of routes.
If a given page did not arrive in a reasonable length of time, one could request that this page be re-sent. Most packet-switched systems allow packets to be discarded if the network capacity is exceeded (the postal system is not supposed to do this). This is accommodated by the higher-level protocol which knows to request that a packet be re-sent if it does not arrive. Therefore, the typical behavior of a packet-switched network when overloaded is that throughput decreases (i.e. the network “slows down”) as the percentage of discarded packets increases. In stark contrast to Circuit Switched networks. See Circuit Switching.
Pair Gain - A method of transmitting multiple POTS signals over twisted pairs. Traditionally used for a single traditional subscriber line in telephone systems. See SLC-96.
PBX - Private Branch Exchange. A privately owned switch. Basically, a PBX is a private “business” telephone system that also interfaces to the telephone network. In some circles, PBX implies a manual switchboard, in contrast to PABX (Private Automatic Branch Exchange) which implies a PBX that supports dialing by end-users.
PIC - Primary Interexchange Carrier. This is your default “1+” carrier used for inter-LATA calls in the U.S. In some cases, you may have two PICs, one for interLATA calls, and one for intraLATA long-distance calls; in this case, it stands for Primary Intraexchange Carrier. In some areas, intraLATA long-distance calls are still handled by your RBOC while in others, you now have a choice. You can identify who your current PIC is by dialing 700- 555-4141.
POP - Point Of Presence. The local facility where your IEC maintains a switch. This is where your long-distance calls get routed so that your IEC can handle them. Also used to describe the local access point of an Internet Service Provider. Sometimes carriers maintain “Paper POP’s”, points of interconnection that are advantageous for regulatory reasons. These are often at Co-Location facilities (COLO’s) or “Telco Hotels”, which are large hardened data centers where many carriers and customers interconnect and terminate data and voice facilities.
Port - This is a pretty general term. Newton’s Telecom Dictionary 10th edition defines a port as “an entrance to or an exit from a network”. Many phone equipment vendors refer to ports as the physical interface between a Switch and a Line or Trunk or “line equipment”. Product literature often refers to the number of ports on a phone system. In this context, it refers to the number of phones or lines (or sometimes the combination) the system supports.
POT - Plain Old Telephone. A black, rotary-dial desk phone. Usually a Western Electric model 500 set. Outdated term.
POTS – Plain Old Telephone Service. Regular old-fashioned analog loop start phone service.
PRI – ISDN Primary Rate Interface. A form of ISDN with 23 “B Channels” and one “D channel”. All 24 channels are carried on a single cable. Functionally related to T1 telephone circuits. In Europe, PRI has 30 “B Channels”, one “D Channel”, and one “Sync channel”. See also B channel and D channel.
Provisioning - The act of configuring a telecommunications service. Also refers to the complete line configuration information.
Bit 1
Bit 2
Bit 3
Bit 4
Telephone Network
OFF
OFF
OFF
OFF
USA, Canada
OFF
OFF
OFF
ON
Japan, low voltage networks
OFF
OFF
ON
OFF
FCC-compliant countries
OFF
OFF
ON
ON
CRT21, Europe (real line impedance)
OFF
ON
OFF
OFF
Custom country configuration
OFF
ON
OFF
ON
Custom country configuration
OFF
ON
ON
OFF
Custom country configuration
OFF
ON
ON
ON
Europe (complex line impedance)
ON
OFF
OFF
OFF
Custom country configuration
ON
OFF
OFF
ON
Custom country configuration
ON
OFF
ON
OFF
Custom country configuration
ON
OFF
ON
ON
Reserved for future use
ON
ON
OFF
OFF
Reserved
ON
ON
OFF
ON
Reserved
ON
ON
ON
OFF
Reserved
ON
ON
ON
ON
Reserved
Bit 5
Bit 6
Bit 7
Bit 8
CPTD Signal Characteristics
OFF
OFF
OFF
OFF
U.S. dial tone ("precise" dial tone)
OFF
OFF
OFF
ON
U.S. re-order signal ("fast busy" tone)
OFF
OFF
ON
OFF
WORLD, single frequency dial tone
OFF
OFF
ON
ON
WORLD, re-order, ON = 155 - 550,
OFF = 155 - 550 ms
OFF
ON
OFF
OFF
WORLD, re-order, ON = 250 - 1200,
OFF = 250 - 1200 ms
OFF
ON
OFF
ON
WORLD, multi-tone dial tone
OFF
ON
ON
OFF
WORLD, multi-tone dial tone
OFF
ON
ON
ON
WORLD, pulse dial tone, ON = 150 - 350,
OFF = 450 - 1100 ms
ON
OFF
OFF
OFF
WORLD, pulse dial tone, ON = 100 - 250,
OFF = 200 - 400 ms
ON
OFF
OFF
ON
Reserved for future use
ON
OFF
ON
OFF
Reserved
ON
OFF
ON
ON
Reserved
ON
ON
OFF
OFF
Reserved
ON
ON
OFF
ON
Reserved
ON
ON
ON
OFF
Reserved
ON
ON
ON
ON
Call Progress Tone Detection (CPTD) feature disabled
Pin
Direction
Unit
Function
1
GPIO Ground
2
GPI
Hybrid 1
Hybrid ON
3
GPI
Hybrid 1
Hybrid OFF
4
GPI
Hybrid 2
Hybrid ON
5
GPI
Hybrid 2
Hybrid OFF
6
GPO
Hybrid 1
Line Ringing Indicator
7
GPO
Hybrid 1
Hybrid In-use Indicator
8
GPO
Hybrid 2
Line Ringing Indicator
9
GPO
Hybrid 2
Hybrid In-use Indicator
USOC – Universal Service Order Code. The Bell System Universal Service Ordering Code (USOC) system was developed to connect customer premises equipment to the public network. These codes, adopted in part by the FCC, Part 68, Subpart F, Section 68.502, are a series of Registered Jack (RJ) wiring configurations for telephone jacks that remain in use today. The now-famous RJ-11 and RJ-45 came from this naming convention.
Variant - The particular protocol (i.e. National ISDN-1 or ETS 300) running on a specific switch. Not all variants are valid for a specific switch. The switch brand and model plus the variant defines the ISND protocol. Applies to configuring the 2101. See ISDN Protocol.
Virtual ISDN - An alternative to repeaters that uses a local Telco Switch to act as a repeater and which then sends the signal onto another switch supporting ISDN. See also Repeater.
VoIP – Voice over Internet Protocol. Communications services that are transported via packet-switched IP networks rather than the public switched telephone network (PSTN).
Work Order - See Trouble Ticket.
Yellow Alarm - An alarm on a T-carrier circuit that is returned by the local equipment if it is in a Red Alarm state. A Red Alarm indicates a loss of inbound signal; a Yellow alarm indicates (indirectly) a loss of outbound signal. See Red Alarm, Blue Alarm, and LOS.
RBOC - Regional Bell Operating Company. Most often called Local Exchange Carriers (LEC’s) at the time of this writing. See CLEC and LEC.
RCF – Remote Call Forwarding, a telephone company service that provides local “virtual numbers” from distant locations. Customers are responsible for the cost of calls forwarded through the RCF number. VoIP service providers can offer similar services at greatly reduced costs since the numbers are delivered via the Internet (“backhauled”) at no cost.
RD - Receive Data. Data coming from the network, or DCE towards the DTE. Also, a light on a modem or CSU/DSU that lights to indicate the presence of this signal.
Red Alarm - An alarm state on a T-carrier circuit that indicates that the incoming signal at the network interface has lost frame for more than a few seconds. Normally a Yellow alarm is then returned (i.e. sent back) if a Red alarm is present. A Red Alarm indicates a loss of inbound signal; a Yellow alarm indicates (indirectly) a loss of outbound signal. See also Yellow Alarm, Blue Alarm, and LOS.
Regional Bell Operating Company - See RBOC or LEC.
Repeater - A device intended to extend ISDN telephone service to sites further from the central office than could normally be served. i.e.: beyond 18,000 feet. ISDN repeater technologies include “BRITE”, “Virtual ISDN”, “Lightspan”, and “Total Reach”. Some Telcos do not use repeaters. Compatibility between a given NT1 (CPE) and a repeater is less certain than if that CPE were directly connected to the switch.
Robbed Bit Signaling - A signaling scheme that “borrows” bits on each T1 channel for use as signaling channels. On SF T1s, there are two bits in each direction: The A bit and the B bit. On ESF T1s, there is also a C and D bit in each direction although they are rarely used. Using these bits, various older analog trunk interfaces can be emulated over a T1. For instance, dial pulse address signaling using 10 pulses per second (rotary style) digit groups over these bits. Since robbed bit signaling interferes with the least significant bit, only 7 bits can be used for sensitive data applications, leaving only a 56kbps channel for data applications. See also CAS and CCIS.
Rollover – See Hunt Group.
SDSL - SDSL is a rate-adaptive Digital Subscriber Line (DSL) variant with T1/E1-like data rates (T1: 1.544 Mbps, E1: 2.048 Mbps). It runs over one pair of copper wires with a maximum range of 10,000 feet. It cannot co-exist with a conventional voice service on the same pair as it utilizes the entire bandwidth of the subscriber loop.
Sealing Current - Unlike telegraphy, teletypewriter, and POTS lines, most digital lines such as ISDN use a voltage mode rather than a current mode of operation. Sealing Current allows a controlled amount of current to be passed through a telecom circuit for purposes of “healing” resistive faults caused by corrosion. Bellcore specifies sealing current on the ISDN U interface in the U.S. The Siemens EWSD switch does not provide sealing current. Most other ISDN-capable switches used in North America do.
SF - Superframe. A type of line format supported on T1 circuits. The Telco determines the line format and line encoding of your line. ESF is the preferred Line Format on T1 circuits. See Line Format.
Silence Suppression - See Statistical Multiplexing.
SIP – Session Initiation Protocol, the most common IP protocol at the time of this writing for providing telephone service over IP facilities. It is used by most Voice Over Internet Protocol (VOIP) service providers.
SLC-96 – A Subscriber Loop Carrier Circuit system manufactured by AT&T (now Lucent). SLC-96 has its own version of T1 framing between it and the CO. SLC-96 and similar “SLIC” systems may or may not perform a concentration function. The interface is the Bellcore TR-008 or the newer GR-303 interfaces that are specialized versions of T1 intended to allow transparent transport of analog CLASS features such as Caller ID, Call Waiting, etc. The GR-303 interface is specifically intended to be used as a common point of interconnection between alternative equipment, technologies, and/or networks (i.e. voice-over-DSL, voice-over-IP, etc.) and the public switched network. See the following link for additional information from Telcordia: http://www.telcordia.com/resources/genericreq/gr303/index.html.
SLIC - Subscriber Line Interface Circuit. See “Line Card”.
SLIC - The equipment used with the AT&T (Lucent) SLCC Subscriber Loop Carrier Circuit, a system used to multiplex a number of subscriber loops onto a single circuit (usually a T1 circuit) to reduce fixed costs.
SLIC - Sometimes used generically for other brands of similar equipment. See also SLC-96.
Smart Jack – See NIU.
SS7 - Signaling System 7. The internationally adopted Common Channel Interoffice Signaling (CCIS) system. Previous to SS7, the Bell System used SS6 which did not support the International Standards. SS7 does. It allows for substantial flexibility and power in dynamically routings calls. An SS7 database lookup is how a call to a mobile telephone user can be handled transparently despite the fact that the user’s location may change. Also used to determine what carrier should handle a given toll free call. See also CCIS.
Station Line – A telephone circuit from a PBX to a telephone on that PBX. Since this is a telephone-to-switch connection, it is considered to be a “line”. See Line and Trunk.
Station Side - The user side of a PBX, that is, the side of the switch to which the telephones are attached. Also, occasionally called the "Line Side." The main reason for distinguishing between this and the trunk side is that certain customer related features (Such as Hold and Transfer) are inapplicable to most trunks. See also Trunk Side.
Statistical Multiplexing - Sometimes abbreviated as "Statmux," a method of improving the effective bandwidth of a Telco channel. Statistical Multiplexing improves efficiency by identifying the many pauses present in a typical conversation, and not sending those pauses. Also referred to as silence suppression. See Circuit Switched.
Subscriber - The customer of a Telecommunications company. This term dates back to when a local Telephone Company was formed at the specific request of a group of customers who agreed in advance to “subscribe” to the service.
Superframe - See SF.
Switch - Telephone switching device that “makes the connection” when you place a call. Modern switches are specialized computers. ISDN service is provided from a “Digital” switch, most commonly an AT&T model “5ESS”, Northern Telecom model “DMS-100”, or Siemens model “EWSD” in the U.S. & Canada. See also PBX.
Switched Circuit - A channel which is not permanent in nature, but rather is connected through a switching device of some kind. The switching device allows a switched circuit to access many other switched circuits (the usual “dial up” type of telephone channels). Once the connection is made however, the complete capacity of the channel is available for use. As opposed to a dedicated circuit or a packet based connection.
Switched-56 - Archaic term referring to a type of digital telephone service developed in the mid 1980’s which allows dialing on a single 56Kbps line. Each Switched-56 circuit has 1 or 2 copper wire pairs associated with it. Switched-56 was replaced with ISDN, which was cheaper and more flexible, and finally by DSL and IP variants. See also CSU/DSU.
Synchronous Data - A form of serial data which uses a clock signal to synchronize the bit stream. Since, unlike with asynchronous data, no start and stop bits are used, data throughput is higher than with asynchronous data. ISDN and T-1 use Synchronous data. See also Asynchro- nous Data.
T1 - A common type of digital telephone carrier widely deployed within the U.S., Canada, and Japan. Has 24 64Kbps channels (called DSØ’s). The most common use for a T1 at the time of this writing is for Telephone company “access service” via an ISDN Primary Rate Interface which 23 “bearer” channels and a single “Data” channel for call set up. A T1 can carry data service only or mixed data and voice when provisioned appropriately, but lower cost services such as DSL are largely supplanting T1 circuits for Internet access.
T-1 - An alternative expression for T1. See T1.
Tandem Switch - A switch which is between two others. It connects two trunks together. Long distance calls on a LEC line go through a long distance tandem that passes them through to the long distance provider’s switch.
Tandem Tie Trunk Switching - The condition when a PBX switch allows a tie line call to dial out of the switch. For example, if switch “A” in Arkansas has a tie line to switch “B” in Boise, Boise could use the tie line to make calls from switch “A”.
TD - Transmit Data. Data coming from the DTE towards the DCE or network. Also, a light on a modem or CSU/DSU that lights to indicate presence of this signal.
Telco - Telephone Company. Your local telephone service provider. In the 21st century, you generally have a choice of Telcos if you are a business in a major metropolitan area in the U.S. Competition is coming to the Telecom industry around the world.
Telcordia Technologies - Formerly Bellcore. The research and development organization owned by the telephone companies. Telcordia represents the phone companies in developing standards for Telco equipment and in testing equipment compliance to those standards. It promotes competition and compatibility through standards, promoting interoperability such as GR-303. Telcordia also offers educational and training programs open to all interested parties. Bellcore was sold to SAIC in 1997. Telcordia is responsive to both RBOCs and independent Telcos. Their web site is: http://www.telcordia.com. See GR-303.
Telephone Number - See DN and MSN.
Telos Customer Support - +1.216.622.0247. Available 24 hours a day, every day. You may also ask for assistance by visiting our website at https://success.telosalliance.com/support.
Tie Line - See Tie Trunk.
Tie Trunk - A Trunk between two PBXs. Note that a Tie Line is a dedicated circuit, not a switched circuit. See Trunk.
TR-008 - See SLC-96.
Trouble Ticket -A Telco “work order” used to track customer repairs within the Telco. If you call someone within the Telco’s repair department, they will need this number to proceed. It will also be needed whenever you call to check on the status of a repair. Always ask for this number when initiating a repair request.
Trunk - A communications path between two switching systems. Note that many trunks may exist on a single circuit (if that circuit has multiple channels). The trunks most users will deal with are between the Telco switch and a PBX. However, a Tie Trunk can connect two PBXs. See also Tie Trunk and Trunk Group.
Trunk Group - A number of telephone channels that are functionally related. Most common is the Hunt Group. Other common types include Incoming Trunk Groups and Outgoing Trunk Groups. See also Combination Trunks and Two-way DID Trunks.
Trunk Side- Central Office - The side of a central office between switches that faces the network. Historically, many CO switches could not make trunk-to-trunk connections, as opposed to tandem and long-distance switches that are always used to connect trunks together. Hence, the need to distinguish between the “line side” and the “trunk side” of the switch. See also Line Side.
Trunk Side- PBX - The side of a PBX that connects to the Telco. Historically, many PBXs could not make trunk to trunk connections, hence the need to distinguish between the “line side” and the “trunk side” of the switch. Since a trunk is a switch-to-switch circuit, these circuits can be called trunks. Beware that even though you have a PBX which may consider these to be "trunks", the Telco may still call these “lines” See also Trunk and Line Side.
Two-way DID trunk - An ISDN PRI equipped for direct inward dialing. Most PBX trunks are related to a given phone number, either alone or as part of a Hunt Group. In the case of a “normal” (i.e. analog) DID Trunk, a group of phone numbers is associated with that DID trunk (or group of trunks) and incoming calls include the DID number so that the PBX can route that call to the correct DID extension. These are one-way (i.e. inward only) trunks. This is exactly how ISDN PRI functions, with the DID information coming in over the D channel. There is a big difference between a normal DID Trunk and a Two-way DID trunk over ISDN PRI. For one thing, ISDN PRI is digital. Another distinction is that you cannot dial out over a true DID trunk, while you can dial out over a PRI (hence the conflicting designation “Two Way Direct Inward Dialing Trunk”).
Two-Wire – A circuit path where only a single pair of wires is used. A hybrid is used to convert from two-wire to four-wire circuits. No hybrid is perfect, and those used by the phone company can be poor. However, the hybrids in Telos Hx units are approaching perfection!
E1 - A common type of digital telephone trunk widely deployed outside the U.S. and Canada. Has 31 available 64 kbps channels (called DSØs) plus a sync/control channel for a total data rate of 2.048 mbps.
E-1 - See E1.
ESF - Extended Superframe. A type of Line format supported on T1 circuits. The Telco determines the line format and line encoding. See Line Format.
Exchange - Another name for a Central Office (most often used in European countries). Also used in the U.S. & Canada to refer to the particular 3-digit prefix of a 7-digit telephone number. See CO.
Extended Superframe - See ESF.
FDL - Facilities Data Link. A bi-directional data link available on T1 circuits when the ESF line format is used. The FDL is primarily used by the Telco to poll the CSU for error statistics.
Four Wire – A circuit path using separate pairs for send and receive. This term is also used when referring to digital channels that inherently have discrete send and receive paths regardless of the number of pairs (or other media) used. See also Hybrid.
Frame – A unit of data which is defined by the specific communications protocol used. See Line Format, T1.
FXO – Foreign Exchange Office termination. A line or port meant to connect to the POTS output of a Central Office. Such an interface goes off- and on-hook to signal status and expects to receive ringing current.
FXS – Foreign Exchange Station termination. A line or port meant to connect to a telephone. Such an interface must look for current flow to know when the attached device goes off-hook. It must be able to generate ringing current. An FXS port will “run a telephone set”.
Glare – On a POTS line, an incoming call is signaled by periodically applying an AC ring voltage to the line. Since there is a semi -andom period before the ring and pauses between rings, it is possible to seize a line that is “about to ring” and thereby answer a call when attempting to place an outgoing call. This scenario is called "glare." Glare is much less likely if Ground Start or ISDN trunks are used. See also Ground Start Trunk.
GR-303 - See SLC-96.
Grade of Service- This is simply the ratio of calls blocked to total calls in a decimal form. Therefore, a grade of service of P.08 would represent 8% blocking. Telephone tariffs regulate the acceptable average grade of service which must be provided on public networks. See also Blocking.
Ground Start Trunk – A type of telephone trunk where the request to make an outgoing call (i.e. request for dial tone) is made by briefly grounding the Tip conductor. Many PBX system use ground start trunks as they are less prone to glare than Loop start trunks. Ground start lines are sometimes used with equipment designed for Loop Start lines. This may or may not work - generally it serves to prevent outgoing calls while incoming calls work normally. Telcos may call these “ground start lines”. See Loop Start Trunk. See also Glare.
GTD-5 - The GTD-5 EAX (General Telephone Digital Number 5 Electronic Automatic Exchange) is the Class 5 telephone switch developed by GTE Automatic Electric Laboratories. This digital central office telephone circuit switching system is used in the former GTE service areas and by many smaller telecommunications service providers. It does not support ISDN.
HDSL - High-Data-Rate Digital Subscriber Line. HDSL delivers 1.544 Mbps of bandwidth each way over two copper twisted pairs. Because HDSL provides T1 speed, telephone companies have been using it to provision local access to T1 services whenever possible. The operating range of HDSL is limited to 12,000 feet and repeaters can be installed to extend the service. HDSL requires two twisted pairs, so it is deployed primarily for PBX network connections, digital loop carrier systems, interexchange POPs, Internet servers, and private data networks. DC voltage used to power the network Interface Unit (NIU) is “phantomed” between the two pairs. See NIU.
Hunt Group - A group of telephone channels configured so that if the first is busy (engaged) the call goes to the next channel. If that channel is busy, it goes to the next channel, etc. Hunt groups may hunt from the highest to the lowest, the lowest to the highest, or in some other arbitrary pattern, but the order of hunting will usually be fixed, beginning with one channel and working through (“hunting”) until an unused channel is found. The term may have originated back in the old manual switchboard days when the operator literally hunted for an unused jack to plug a cord into. This arrangement is very common in business scenarios where a single incoming number (the Listed Directory Number) is given to the public, but multiple incoming channels are supported. See also LDN.
Hybrid – A device which converts from a two-wire signal such as POTS lines or a 2-wire intercom to a four-wire system with separate send and receive paths such as used in the pro audio world. While this task is theoretically quite simple, the fact the impedance of most phone lines varies widely across frequency complicates matters. The Telos 10 telephone system was the first practical DSP based hybrid and applied the then brand-new technology to this problem.
IEC - Inter-Exchange Carrier. “Long Distance” carrier. Handles InterLATA and interstate calls. Most often referred to as IXC.
IEC - International Electrotechnical Committee. A European standards body best known for the power plug now used throughout the world for AC power cords on office equipment and computers.
ILEC – Incumbent Local Exchange Carrier. A local Exchange Carrier that entered the marketplace before the enactment of the 1996 Telecom act, i.e. a telephone company which is neither an Independent nor an RBOC. See LEC and CLEC.
IMUX – See Inverse Multiplexing.
In Band Signaling- A signaling system where network information such as address and routing information are handled over the communications (voice) path itself. Usually the information is represented in the form of audible tones, however DC loop current signaling also qualifies as In Band Signaling. See also CCIS.
Incumbent Local Exchange Carrier - See ILEC. See also CLEC & LEC
Independent – Any of the phone companies in existence at the time of divestiture that were not affiliated with the Bell System. See RBOC, LEC, and CLEC.
Indi - See Independent.
Interconnect Company - A vendor of telecommunications CPE other than a BOC or AT&T. This term was originated by AT&T and was meant to be derisive towards the fledgling industry when the courts said it was OK for end users to buy equipment from someone other than the Bell System. This industry flourished, in spite of AT&T’s disdain, and ironically, the RBOCs were not allowed to sell CPE under the terms of the break up of AT&T. With the current state of deregulation, the RBOCs are slowly re-entering this business. The term is now considered archaic at the time of this writing.
Inter-exchange Carrier - See IEC.
Interwork - The ability of two different type of networks to communicate seamlessly. For example, ISDN can interwork calls to both a POTS network and a Switched-56 network.
ISDN - Integrated Services Digital Network. A relatively new and highly flexible type of telephone service which allows dialing on digital channels with multiple bi-directional “bearer” channels each with a capacity of 56 or 64 Kbps and a single bi-directional “D channel”. See BRI and PRI.
ISDN Protocol - The “language” used for communication between the Telco’s switch and the customer’s Terminal Adapter. Each ISDN circuit has one protocol, and the protocol has no effect on where or whom one may call. See ETS 300, National ISDN, and Custom ISDN.
ISDN 2 - A term used in Europe for ISDN BRI. Also called SØ. Not to be confused with National ISDN-2. See BRI.
ISDN 30 - A term used in Europe for ISDN PRI. Also called S2M. See PRI.
ISG – Incoming Service Grouping. A Hunt Group. See Hunt Group.
IXC - IntereXchange Carrier. See IEC.
Kbps - KiloBits Per Second. Measure of digital channel capacity.
Key Telephone System – A system that allows multiple telephones to share multiple pre-determined telephone lines. The system provides indicators to allow the user’s to understand the status of each line available on a given phone. In its most basic form it is up to the user to provide the intelligence to select an unused line, or answer a ringing line, for example. See also PBX.
LATA- Local Access and Transport Area. The area within which calls are routed by your Local Exchange Carrier (LEC). Under the divestiture of the Bell System, calls going outside of this area must be handled by an Interexchange carrier (IEC). With the latest round of de-regulation the usual IEC companies are being allowed to compete in the IntraLATA long-distance market and LECs are beginning to be permitted to handle InterLATA calls.
LDN - Listed Directory Number. When a number of Telco channels share the same hunt group, it is customary to give out only one phone number for the group although generally, each channel will have its own number. The number given out is the “Listed Directory Number” since that is the number that would be listed in the Telephone Directory and given to customers. Sometimes called a Pilot Number. See also DN and Hunt Group.
LE - Local Exchange. European term for Central Office. See CO.
LEC- Local Exchange Carrier. Your local telephone service provider which is either an RBOC or an Independent. In other words, a traditional phone company. In contrast to CLEC or IEC.
Line - An electrical connection between a telephone service provider’s switch (LEC or CLEC) and a telephone terminal or Key system. In contrast to a Trunk, which is an electrical connection between a telephone service provider’s switch and another switch. Note that some types of physical lines offer more than one channel such as a BRI circuit which has 2 channels, called B channels. This term is a confusing one, so we try to avoid using it. See Channel. See also Station Line.
Line Card - The circuit in the Telco switch to which your line is connected. On an ISDN circuit, the line card performs a role analogous to the NT1 in adapting to and equalizing the circuit to establish OSI Layer 1.
Line Coding, T1 - The clock signal for T1 is derived at the far end from the data bits themselves. Therefore, T1 lines have certain restrictions as to the data allowed. No more than 15 zeros shall be sent in a row, and an average density of 12.5% ones must be maintained. The CSU is responsible to ensure these requirements are met. The line encoding method, either AMI or B8ZS, determines exactly how these requirements are met while still allowing recovery of the original data at the far end. Your Telco will determine the method used on a specific circuit. B8ZS is preferred. E1 circuits have similar restrictions. HDB3 is preferred for E1 circuits.
Listed Directory Number - See LDN.
Line Equipment – The circuit on a telephone company’s switch that is used to provide service to a customer.
Line Encoding, T1 - See Line Coding, T1.
Line Format, T1 - Modern T1 circuits usually use either Superframe (sometimes called SF or D4) or Extended Superframe (sometimes called ESF) line formatting. The type of framing used is determined by your Telco. ESF is preferred. See ESF and SF.
Line Side - This is the side of a central office switch to which the subscriber’s telephone lines are connected, i.e., the user side of a PBX. Also called the Station Side. The main reason for distinguishing between this and the trunk side is that certain customer related features (Such as CLASS and Centrex features) are inapplicable to trunks. See also Trunk Side.
Line Termination - See LT.
Local Access and Transport Area - See LATA.
Local Exchange Carrier - See LEC and CLEC.
Long Distance - If your local U.S. Telco is a former Bell Operating Company, then any call outside of your LATA or any Interstate call is considered long distance and is handled by an IEC. The above is true regardless of whether you are referring to a dedicated line or a dial-up call. However, under the current state of deregulation, toll calls within a LATA may now be covered by the IXC, and in some cases RBOCs are being permitted to handle InterLATA calls. These requirements are largely ignored at the time of this writing.
Loop - The telephone circuit from the CO to the customers premises. Generally refers to a copper cable circuit.
Loop Current Disconnect Supervision - Another name for CPC. See CPC.
Loop Qualification - The process of actually measuring the loss on a prospective ISDN line to see if it can be used for ISDN service. The actual loss on the line (usually measured at 40 kHz) is the determining factor as to whether ISDN service can be offered without a repeater. Generally, ISDN or DSL is available up to 18,000 feet from the serving Central Office. It may not be available within this range, or may be available further from the CO. Only a loop qualification can tell for sure. Not all Telcos will extend ISDN lines with repeaters.
Loop Start Line - A plain old telephone line. The telephone terminal signals the “off hook” condition by allowing DC current to flow. See Ground Start Trunk. See also Glare.
Loop Start Trunk – A plain old telephone line connected to a PBX switch. The PBX signals the “off hook” condition by allowing DC current to flow. Ground Start Trunks are generally preferred for use on PBXs to prevent glare. Also, most trunks are considered “designed circuits” which means that only a specified amount of loop loss is permissible, and the telephone company is required to deliver the trunk to the customer at a given audio level. At the time of this writing, analog trunks are rapidly becoming less common as they are expensive to design, provision and maintain. See Loop Start Line. See also Ground Start Trunk. See also Glare.
LOS - Loss Of Signal. An LED or other indicator that illuminates if a signal is absent. This terminology is commonly used with T-1 equipment. See Red Alarm.
LT - Line Termination. The electrical and protocol specifications for the Central Office end of an ISDN line. If you wish to connect an ISDN terminal (such as a Zephyr Xstream) to a PBX, the PBX must support LT ISDN. See also NT and Line Card.
Lucent Technologies - The company that made the former AT&T 5ESS switch as well as various other pieces of Telco gear and semiconductors. Lucent was split off from AT&T in 1996. Lucent’s PBX division was spun off in 2001 as AVAYA.
You’ll get better results from the Telco if you understand and speak the lingo, so we have tried to include the most typical and commonly-used acronyms used by Telco personnel here with their definitions.
1MB – USOC term for a single Measured Business line in the US. See USOC.
1FB – USOC term for a single Flat Rate Business line in the US. See USOC.
1FR – USOC term for a single Flat Rate Residential line in the US. See USOC.
5ESS - The 5ESS Switch is a Class 5 telephone electronic switching system sold by Alcatel- Lucent. This digital central office telephone circuit switching system is used by many telephone companies. It is one of the most common Central Office switches used in the US.
Analog Terminal Adapter - A device used to connect one or more standard analog telephones (POTS) to a digital telephone system (such as a Voice over IP network) or a proprietary telephone system such as a PBX or Key System.
ADSL – Asymmetrical Digital Subscriber line. The most common type of telephone company delivered Internet access. The download/downstream direction is usually at a higher rate than the upload/upstream direction. Most often installed as “Line Share DSL”, that is the DSL “rides on top of ” the POTS line. “Dry Pair DSL” is usually available for customers desiring only the data service. Service availability is limited by loop length and cable type.
AMI – Alternate Mark Inversion. A T1 line coding method. See Line Coding, T1. Also see B8ZS.
ANI – Automatic Number Identification. A system originally designed for use by Interexchange carriers (IXCs) that transmits the “billed party number” along with a call. Note that the billed party number is not necessarily the number of the line placing the call. ANI predates SS7 and can operate with analog as well as digital trunks. See CLID. Also see Caller ID.
Asynchronous Data - A form of serial data communication that is not clocked. To keep the bitstream synchronized, start and stop bits are added which cuts down on throughput. RS-232 computer data is commonly asynchronous data. In contrast to synchronous data.
ATA – See Analog Terminal Adapter.
B8ZS- Bipolar 8 (with) Zero Substitution. A T1 line coding method. This is the more modern and most common line coding method of the two commonly available. See Line Coding, T1. Also see AMI.
Behind the PBX- This is our own term and refers to when one privately owned phone system is tied to another privately owned phone system. The most common application is when a key system is connected to the analog ports of a PBX. When it involves one PBX behind another, it is a limited Tandem application. See Tandem Switch. Also see Tandem Tie Trunk Switching.
Bell Operating Company. Most often called “LEC’ (Local Exchange Carrier) at the time of this writing. Few companies use the Bell name in the U.S any longer, though it is used in Canada. See BOC. See also RBOC.
Bellcore- Bell Communications Research. The research and development organization owned by the RBOCs. Bellcore represents the RBOCs in developing standards for Telco equipment and in testing equipment compliance to those standards. Bellcore also offers educational and training programs open to all interested parties. Now Telcordia. See Telcordia.
BERT - Bit Error Rate Test. A test for digital lines involving looping a data path and sending a test pattern. Data returning is compared to the sent data to check for errors. Depending on the “Test Pattern” used, BERTs may or may not uncover problems. A line that only has occasional problems will need a BERT of sufficient time duration to catch the intermittent problem. A five-minute BERT of an ISDN BRI circuit will only catch severe problems. BERT may also refer to a Bit Error Rate Tester, the test equipment used to perform a Bit Error Rate Test.
Billing Telephone Number - The main phone number to which all calls on hunt group or a PRI are billed. This information may be required when configuring a PRI PBX.
Bit Error Rate - The basic measure of errors on digital transmission paths, usually expressed as the number of errors per number of bits.
Bit Error Rate Test - See BERT.
Bit Rate - The capacity of a digital channel. See Kbps.
BLEC - Building Local Exchange Carrier. An LEC who covers the occupants of a single building (or a small group of buildings) only. Often Telecom services are provided by a BLEC as a service or incentive to potential tenants. If a BLEC offers Long Distance Service it is covered by the same regulations as any other LEC.
Blue Alarm - Also called an Alarm Indicating Signal (AIS). A keep-alive signal sent if a problem occurs mid-span in a T-carrier system. The blue alarm signal is required because in some cases T-1 repeaters will become unstable if inadequate 1’s density is not maintained.
BOC - Bell Operating Company. One of the regional telephone companies that were owned by AT&T before divestiture in 1984 (i.e. New England Telephone, Ohio Bell, etc). The 22 BOCs were divided among the Regional Bell Operating Companies at divestiture. See RBOC.
Both Way Trunks - See Combination Trunks.
BTN- See Billing Telephone Number.
Business Office - The part of the phone company that you call if they mess up your bill, to report problems, and to order service. Not necessarily technically literate.
Caller ID - A CLASS feature on an analog line that provides the number of the calling line as a burst of FSK data (Bell 202 modem tones) following the first ring. Also called Calling Line Identification. See CLASS.
Calling Line ID - See CLID. Also see Caller ID.
Calling Party Control - See CPC.
Call Progress Tones – Tones used in the telephone network to indicate call status or progress through the network. This includes dial tone, ring-back tone, and re-order (fast busy) tone, Special Information Tones (SIT’s), etc. The Telos Hx can be set to listen for these tones and disconnect when one is heard if CPC is not available or is unreliable.
CAS - Channel Associated Signaling. A bit-based signaling method used on digital lines (such as T1) that is periodically inserted into the low order bit that is also used for the audio transmission. See Robbed Bit Signaling.
CCIS - Common Channel Interoffice Signaling. A signaling system where network information such as address and routing information are handled externally to the actual communications (voice) path. SS7 (Signaling System 7) is the internationally standardized CCIS system.
Deployment of CCIS increased efficiency since no communications (voice) channels are used merely to report “all trunks busy” or “far end busy” conditions. It also decreased toll fraud substantially since it removed the potential for access to the signaling information that was inherent to in-band signaling schemes. CCIS also enables CLASS features as well as sophisticated re-routing features for “intelligent network” applications. Also see In-Band Signaling and SS7.
Central Office - See CO.
Centrex - Central Exchange Service. An enhanced business telephone service intended to offer most of the features of a PBX but where the lines are all from the LEC out of a public switch. Offers CLASS-like features for business users such as 4-digit “inside” dialing, hold, transfer, attendant, etc.
CEPT- Conference on European Posts & Telecommunications. This is a European standards body that formerly set the standards for telephone interfaces for 26 countries.
CEPT Format - The usual rate and frame format for E1 circuits (2.048 mbps). Also see E1.
CEPT Rate- See CEPT Format. Also see E1.
Channel Associated Signaling - See CAS. Also see Robbed Bit Signaling.
Channel Bank - A device that multiplexes or demultiplexes a group of communications channels, such as analog or digital telephone lines, into one channel of higher bandwidth or higher digital bit rate such as a DS-1 (T1) circuit. Also see Pair Gain.
Choke Exchange - A telephone exchange assigned to Radio and TV stations, promoters, and other users that will be receiving large numbers of simultaneous calls. The idea is to group all of these users on a single exchange so when all routes into that exchange are in use, “normal” users (on other exchanges) will not experience blocking of incoming or outgoing calls.
Trunks from other local exchanges into the choke exchange are deliberately limited to just a few paths so callers will get an “all trunks busy” instead of completely blocking their local exchange. However, when one of the choke exchange users experiences a large number of calls (as when your station runs a contest) the other choke exchange users will be blocked because all trunks into the choke exchange will be busy.
In the modern network, using CCIS signaling such as SS7, actual trunks are not used to convey “busy” or “all trunks busy” conditions. Thus blocking due to a station contest should not occur as the busy status in response to a call attempt is conveyed over the separate SS7 network. Therefore, the need for choke exchanges has pretty much disappeared. Nonetheless, many Telcos still insist that broadcasters use special choke lines for call-in lines. Much of the need for the “choke network” is historical, but few current telephone company employees understand this concept and only seem to believe that it is “required”.
Unless very aggressive contesting is planned, these arrangements should probably best be avoided. See blocking and concentration.
Circuit - A physical path through which electrical signals can pass. It consists of a network of conductors and other components, separated by insulators. Technically this term cannot be applied to fiber optic or other “non-metallic” paths. Also see Channel.
Circuit Switching - A system where a dedicated channel is allocated to the users of that call for the duration of that call and regardless if the information is being transmitted at any given moment. Bandwidth through the channel is fixed, and at no time may this bandwidth be exceeded. If this bandwidth is not used, it is wasted.
While inherently inefficient, the dependable and reliable nature of circuit switching makes it ideally suited to real-time voice and audio/video conferencing applications.
When over-loaded Circuit Switched networks will respond “all circuits are busy… try again later”. This is in stark contrast to Packet Switched networks or to systems where statistical multiplexing (Statmux) is used. See Statistical Multiplexing. Also see Packet Switching.
CLASS - Custom Local Area Signaling Services. A variety of enhanced features (usually on analog lines) that take advantage of the ability of modern SS7 technology’s ability to transmit information about the calling party. CLASS includes such features as Caller ID, Automatic Callback, Call Trace (initiated by subscriber), Selective Call Screening, etc.
Class 4 Switch - A Class 4, or Tandem, telephone switch is a U.S. telephone company central office switch used to connect local exchange (Class 5) central offices for long distance communications in the Public Switched Telephone Network. See Class 4/5 switches.
Class 4/5 Switch – Also called a “Hi/Lo” switch. This is a U.S .telephone company central office switch that provides both local and long distance service. Many CLEC’s are configured in this way. See Class 4 or Class 5 switches.
Class 5 Switch - A Class 5 telephone switch is a telephone switch or telephone exchange in the Public Switched Telephone Network located at the local telephone company’s central office, directly serving subscribers. Services provided include basic dial-tone, calling features, and additional digital and data services to subscribers using the local loop. It is considered a “local switch’.
CLEC - Competitive Local Exchange Carrier. Your local telephone service provider, and one of the new-generation providers rather than an RBOC or Independent. A CLEC is really just an independent, albeit one formed after the divestiture of AT&T. See LEC. Also see Independent.
CLI - Calling Line Identity. European term for CLID. See CLID.
CLID - Calling Line Identification. This is the ISDN and SS7 equivalent of Caller ID, that is, the number of the calling party. Also see Caller ID and ANI.
CO- Central Office. The Telco facility to which your local telephone circuits lead. Contains “Switches” and “Trunks” as well as the local telephone circuits.
Codec- COder/DECoder. A device that takes digitized audio and “codes” it in order to reduce the transmission bit rate. It can also simultaneously “decode” such coded audio.
Strictly speaking, a codec does not include an ISDN terminal adapter and related equipment. Simple codecs are also used in digital telephony that employ simple companding schemes to reduce channel noise.
COL - COnnected Line number. A European term referring to the number to which you have connected. This may not be the number you dialed if call forwarding is used.
Combination Trunk - A trunk (channel) that can both make and receive calls. This generally refers to analog ground start or loop start trunks, although the term can be applied to ISDN BRI or PRI channels as well. Each combination trunk normally has a telephone number, although they are frequently part of a hunt group and only one number may be published for that group. Also called a Both Way Trunk. This is not the same as a Two-way DID trunk. See Trunk, Hunt Group, and DID Trunk.
Common Channel Interoffice Signaling - See CCIS.
Competitive Local Exchange Carrier- See CLEC.
Concentration- The basic premise is to share facilities wherever possible. For instance, while there may be thousands of customers served by a given Central Office, there will be substantially fewer calls that can be handled simultaneously, and even fewer long-distance calls. The art of Traffic Engineering is to have enough capacity that calls are rarely blocked, but no more than that number. See also Choke Exchange and Blocking.
CPC - Calling Party Control. Sometimes referred to as “CPC Wink” or “disconnect supervision”. A call supervision feature on an analog loop start line that provides the ability for a CO (Central Office) to signal the called party when the calling party hangs up. CPC allows the PBX, key system, or telephone answering device to reset the line so that it is ready to accept or initiate another call. CPC is accomplished by either a loop current drop or reversal. With some CO equipment, it is also provided if the called party drops the call. See also MCLD.
CPE - Customer Premise Equipment. Customer-owned equipment located at his/her facility, such as a CSU or terminal. In the U.S. and Canada, the ISDN NT1 is part of the CPE.
CPN - Called Party Number. European term for the number that has been dialed. See Called Party Address.
CSU - Channel Service Unit. The NCTE used in the U.S. & Canada to terminate a T1 line. Typically the CSU must be provided by the end-user. See NCTE, NIU, and DSX1.
CSU/DSU - A device which incorporates the functions of a CSU (Channel Service Unit) and a DSU (Data Service Unit). Most commonly it interfaces between a Switched-56 or Dedicated Digital Service circuit and a user’s data equipment such as the Zephyr.
D4 - See Superframe. See also Line Format.
DCE - Data Communication Equipment. When using serial communications such RS-232, V.35, or X.21, the DCE is the device sending/receiving from the Telco line. i.e.: a modem or CSU/DSU. In contrast to DTE.
Dedicated Circuit - A permanent channel between two locations. As opposed to a Switched Circuit.
Demarc – The point of “Demarcation," that is, where the telephone company’s responsibility ends and the customer's begins. Most often located in “the main phone closet” or basement terminal. At one time, a special block was required for a Demarc, one for each customer, with a simple way to disconnect the customer's wiring from the Telco’s wiring at the demarc point. This practice has been abandoned. When you order service today, it will be “to the demarc” only and the telco will (usually) provide a tag or “cable and pair” number so that you can locate the circuit in question. Residential phones still have a demarc in the form of a box (usually gray) mounted to the side of the house. It most often provides remote line disconnection facilities (for remote testing by the phone company) and a customer-accessible modular jack to allow the customer to verify proper operation of the line at the side of the house before the house wiring.
DID - Direct Inward Dialing. The ability for an outside caller to dial to a PBX extension without going through an attendant or auto-attendant. See also DID Number and DID Trunk.
DID Extension or DID Station - A specific phone within a PBX that can be called from the public telephone network without going through an attendant or auto-attendant.
DID Number - A phone number used to route calls from the telephone network to a specific phone in a PBX (the DID extension). DID requires special DID trunks or ISDN PRI “two- way DID” trunks. Blocks of DID numbers (typically 10 or 20, sometimes higher) are purchased from the LEC or CLEC for use on the PBX. The number of DID numbers usually substantially exceeds the number of trunks in the system.
DID Trunk - A Direct Inward Dialing Trunk. A trunk (channel) that can only receive calls. A group of telephone numbers (DID numbers) are associated with a given trunk group, however, there is no one-to-one correspondence between the individual channels and these numbers. The PBX uses the DID number given by the phone company to route the channel to the correct DID extension within the PBX. This allows some or all PBX stations to receive calls directly without going through an attendant or auto-attendant. Note that there are usually more DID numbers than there are DID trunks. See DID number and DID extension.
Direct Inward Dialing - See DID.
Directory Number (U.S. & Canada)- Your seven-digit telephone number (without the area code) as found in the telephone directory.
DMS-100 – Nortel’s very popular central office switch that provides local POTS service and connectivity to the public switched telephone network. It is used widely throughout the world.
DNIS - Dialed Number Identification Service. A service, typically offered by a long-distance company on 800 lines, that provides the number dialed by the caller. This allows a caller to receive specific treatment depending on the number dialed.
DP - Dial Pulse. A method of sending address information by either causing brief inter- ruptions in loop current, or causing brief changes of state of a bit on a digital circuit using Channel Associated Signaling. In other words, “rotary” or “pulse” dialing. See also DTMF and CAS.
Dry Loop or Dry Pair DSL – DSL service offered without a POTS line to carry it. These circuits often cost less because many of the taxes, “regulatory recovery fees” and other nonsense charges apply only to POTS phone service. Also, many customers wish to use VoIP with their DSL and have no use for the expensive POTS phone once required to be ordered with DSL service.
DSØ - Digital Signal Level Zero. At 64 kbps, he smallest unit of measure of the standard rate hierarchy used by the Telcos (i.e. all other rates are a multiple of the DSØ rate). For example, the T1 rate is 24 times the DSØ rate and the E1 rate is 32 times the DSØ rate. See also B channel.
DS1- Digital Signal Level 1. The second level up the digital rate hierarchy used by the Telcos. This is 24 times the DSØ rate for a total of 1.544 mbps. See DSØ. See also T1.
DS2 -Digital Signal Level 2. Provides a data rate of 6.312 mbps (4 times the DS1 rate). See DSØ and DS1.
DS3 -Digital Signal Level 3. Provides a data rate of 43.232 mbps (28 times the DS1 rate). See DSØ and DS1.
DSL - Digital Subscriber Line. Traditionally refers to an ISDN circuit or sometimes a T1 line, although the term is also frequently used to mean the next generation beyond ISDN. Sometimes xDSL is used to indicate a reference to any of a number of emerging DSL technologies.
DSLAM – Central Office or wire center-based Digital Subscriber Line Access Multiplexer, aka what's on the “other end” of your DSL line. These are sometimes fed by HICAP (High Capacity or Fiber) facilities to remote wire centers (“remotes” or “vaults”) where “Pair Gain” (carrier) systems reside so that DSL service may be provided to customers who otherwise could not be served due to loop length limitations.
DSU - Data Service Unit. See CSU/DSU.
DSX-1 - Digital Cross Connect Level 1 (U.S. & Canada, primarily). Defined as part of the DS1 (T1) specification and a closely related signal. The type of signal switched by a Digital Cross- Connect System (DACS). The FDL is stripped off at the DACS interface. DSX-1 is also the type of signal that arrives at the user side of a CSU on a T1 line. A DSX-1 cable is limited to 655 feet (200 meters).
DTE - Data Terminal Equipment. When using serial communications such RS-232, V.35, or X.21, the DTE is the device sending/receiving from a modem or CSU/DSU. In contrast to DCE.
DTMF - Dual Tone Multi Frequency. The standard tone-pairs used on telephone terminals for dialing using in-band signaling. The standards define 16 tone-pairs (0-9, #, and A-F) although most terminals support only 12 of them (0-9 and #). These are also sometimes referred to as “Touch Tones”. Note that while digital data terminals have the same symbols, ISDN uses “common channel signaling” (over the D channel) and therefore does not necessarily generate any tones at all. However many terminals still generate the tones since they will still be used on occasion to access services such as voicemail or an automated attendant at the far end using in-band tones. The extra 4 tones were originally used in the U.S. military “Autovon” phone network.
SETTINGS | Function |
Bit 1 | Bit 2 | EQ LO, Fixed dB Gain Adjustment |
OFF | OFF | 0 dB adjustment (factory default setting) |
OFF | ON | +2 dB adjustment |
ON | OFF | +4 dB adjustment |
ON | ON | +6 dB adjustment |
Bit 3 | Bit 4 | EQ HI, Fixed dB Gain Adjustment |
OFF | OFF | 0 dB adjustment (factory default setting) |
OFF | ON | +2 dB adjustment |
ON | OFF | +4 dB adjustment |
ON | ON | +6 dB adjustment |
Bit 5 | Bit 6 | Ducker dB Gain Adjustment |
OFF | OFF | Full Duplex (no attenuation) |
OFF | ON | -6 dB attenuation (factory default setting) |
ON | OFF | -12 dB attenuation |
ON | ON | Half Duplex |
Bit 7 | Bit 8 | AGC and Noise Gate Settings |
OFF | OFF | Phone AGC = OFF, Noise Gate = OFF |
OFF | ON | Phone AGC = 1/2 Full, Noise Gate = OFF |
ON | OFF | Phone AGC = Full, Noise Gate = OFF (factory default setting) |
ON | ON | Phone AGC = Full, Noise Gate = Normal |
OPTIONS | Function |
Bit 1 | Bit 2 | DDEQ Configuration |
OFF | OFF | DDEQ = OFF |
OFF | ON | Fixed EQ (Use SETTING Bits 1-4 to set levels) |
ON | OFF | Adaptive EQ (factory default setting) |
ON | ON | Adaptive + Fixed EQ (Use SETTING Bits 1-4 to set fixed levels) |
Bit 3 | Bit 4 | Auto-Answer Configuration |
OFF | OFF | Auto-Answer = OFF (factory default setting) |
OFF | ON | Auto-Answer = ON, Auto-Answer after first ring |
ON | OFF | Auto-Answer = ON, Auto-Answer after third ring |
ON | ON | Auto-Answer = ON, Auto-Answer after eighth ring |
Bit 5 | Send Additional Gain to Caller |
OFF | No additional gain applied (factory default setting) |
ON | +3 dB additional gain applied |
Bit 6 | Hx2 Internal Mix-Minus Enable |
OFF | Disabled, Independent Mode (factory default setting) |
ON | Enabled, Coupled Mode |
Bit 7 | Feedback Reduction Enable |
OFF | Acoustic Echo Canceller disabled (factory default setting) |
ON | Acoustic Echo Canceller enabled |
Bit 8 | Reserved |
OFF | Reserved for future use (default factory setting) |
ON | Not recommended |