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AT&T 555-600-736 - page 1
AT&T MERLIN LEGEND™ COMMUNICATIONS SYSTEM APPLICATION NOTES MERLIN LEGEND™ COMMUNICATIONS SYSTEM Applications Note On Basic Trunking Concepts Abstract This Application Note describes the various types of trunks that link the MERLIN LEGEND Communications System with the telephone network. Operating characteristics of the various trunks are s ...
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AT&T 555-600-736 - page 2
Issued January 1992 Copyright 1991. AT&T 555-600-736 Jim Pastorius Kevin Lyons Writers/Editors Contributors: A. Cohen D. Guerro V. Illuzzi R.G. Koppenheffer D. Margolis S.W. Osborne H.T. Reeve M. Stevenson B. Tannu C.A. White J. Webb ...
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AT&T 555-600-736 - page 3
MERLIN LEGEND TRUNKING CONCEPTS APPLICATION NOTE INDEX Introduction Tip & Ring Explained Lines & Trunks Loop-Start Trunks Operations Potential Problems When to Use L/S Ground-Start Trunks Operations Potential Problems When to Use G/S Direct Inward Dialing Operations Signaling Characteristics LEGEND Operation Administration When to Use DID T ...
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AT&T 555-600-736 - page 4
-2- INTRODUCTION TO TRUNKING CONCEPTS The way lines and trunks have been used to meet customers’ needs over past decades is rapidly changing. T-1, ISDN technology, fiber optics, and other advances in telecommunications are forcing us to rethink what lines and trunks should be used for a PBX or Key system. It is critical, however. that everyone in ...
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AT&T 555-600-736 - page 5
-3 - LINES AND TRUNKS Telephone lines and telephone trunks are facilities that carry voice or data communications. They are similar in form and function, and the two terms are usually treated as if they are interchangeable. The fundamental difference between a line and a trunk is that a line connects a station instrument to a switching system, and ...
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AT&T 555-600-736 - page 6
-4 - LOOP-START TRUNKS: OPERATIONS Loop-start facilities are the simplest and most common end-user facilities in the nation-wide telephone network. Loop-start facilities provide virtually no supervision between the central office and the customer premises equipment (CPE). For this reason, loop-start facilities are usually suited for use with teleph ...
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AT&T 555-600-736 - page 7
-5 - LOOP-START TRUNKS: POTENTIAL-PROBLEMS The most common application for loop-start facilities is single line residential service. Many of the disadvantages of a loop-start trunk in a PBX environment can be inferred from the operation of a loop-start residential telephone line, like the one you have at home. The Problem of Glare Perhaps, at least ...
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AT&T 555-600-736 - page 8
-6 - The ARS feature also isolates the station user from the specific trunk, and even the group of trunks. that carries each outgoing call. Other features. such as Callback Queuing (LEGEND) or Busy-to-Idle (System 25) reminders, allow station users to seize trunks moments after a previous conversation concludes, and easily fast enough to beat a rin ...
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AT&T 555-600-736 - page 9
-7 - LOOP-START TRUNKS: WHEN TO USE LOOP-START TRUNKS There are two times when you consider the use of loop-start facilities: when you should use loop-start facilities and when you must use loop-start facilities. Proper Loop-Start Facility Applications If loop-start facilities are prone to problems such as glare why are they still in use? Most of t ...
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AT&T 555-600-736 - page 10
-8 - Cost Unfortunately, the most common reason for using loop-start trunks is the least valid. This reason is cost. If a customer currently has a key system, service at that location is undoubtedly supplied by loop-start lines. Converting the lines to ground-start trunks may involve a longer installation intend, and may incur additional charges fr ...
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AT&T 555-600-736 - page 11
-9 - GROUND-START TRUNKS: OPERATIONS Ground-start facilities were specifically introduced to solve the problems that PBXs encounter on loop-start trunks. A ground-start facility provides an immediate signal when it is seized and it provides a positive signal when one party disconnects. When a ground-start facility is idle the CO provides battery vo ...
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AT&T 555-600-736 - page 12
-10- GROUND-START TRUNKS: POTENTIAL PROBLEMS There are very few problems that can occur when properly functioning ground-start trunks serve a properly administered PBX, since modem PBXs and ground-start trunks were literally made for each other. This Application Note does not cover the kinds of problems that can occur when a trunk develops a proble ...
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AT&T 555-600-736 - page 13
-11- DIRECT INWARD DIALING (DID) TRUNKS: OPERATIONAL CHARACTERISTICS Loop-start trunks and ground-start trunks are simple, two-way local facilities, i.e., they can handle incoming and outgoing calls. The operation of loop-start and ground-start trunks can be understood by analogy to the residential service in your your home. Direct Inward Dialing ( ...
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AT&T 555-600-736 - page 14
-12- Once a trunk has been seized -- the PBX has been alerted to the incoming DID call, and the addressing information has been sent -- there are three possible responses from the PBX. a. The PBX will return an audible ringing signal if the desired voice terminal is available, if the call can be routed to a coverage position or attendant, or if the ...
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AT&T 555-600-736 - page 15
-13- Outpulsing methods, it seizes a trunk by closing the loop and allowing current to flow. When the PBX recognizes the trunk seizure from the CO it responds by reversing the battery and ground on the Tip and Ring leads. On delay-dial trunks this signal is called the delay-dial signal. On wink-start trunks this reversal, going from an on-hook cond ...
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AT&T 555-600-736 - page 16
The options for each trunk group are as follows: * DID Trunk Protocol *Wink start (default) -14- ● immediate start * Dial Mode * pulse (default) ● tone * Expected Number of Digits * 3 (default) *0 to 4 * Number of Digits to Add * 0 (default) * 0 to 4 CONSIDERATIONS IN USING DID TRUNKS DID trunks are reliable and efficient, but they are more com ...
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AT&T 555-600-736 - page 17
-15- WHEN TO USE DID TRUNKS DID trunks provide fast access to specific individuals. DID trunks should be considered when a customer has sales people who work with assigned territories, service people who work with ‘assigned accounts, or any other organization seeking personal accountability. DID trunks, especially when combined with station featu ...
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AT&T 555-600-736 - page 18
-16- (There will be some Of course, these tie ordinary tie trunks. In special cases, tie trunks are used to join one PBX directly to another PBX. This may occur if multiple PBXs serve a single-customer at a single location. A typical example would be a corporate headquarters consisting of several buildings, each housing a separate division, co-loca ...
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AT&T 555-600-736 - page 19
-17- TIE LINES: Transferring Calls The MERLIN LEGEND CS supports trunk calls that come into the system and go out on another trunk without any operator assistance. However, the transmission code in the system does not permit multiple hops, and there is no automatic routing system which can be used for tandem trunking. Never-the-less, with the LEGEN ...
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AT&T 555-600-736 - page 20
-18- In order to approach a.LEGEND system implementation with tie trunks it is really only necessary to know which signaling formats are supported and to determine which of these supported formats are required. The LEGEND system with the 400EM module supports Type 1 E&M Standard, Type 1 E&M Compatible, and Type 5 tie trunks. The transmit an ...
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AT&T 555-600-736 - page 21
-19- OFF PREMISES STATIONS On occasion, customers need to locate telephones away from the principal area of the PBX or Key system terminal concentration. The telephone can use an off-premises or out-of-building arrangement. There is a major difference between the two types. An off-premises telephone (OPT) is a single-line set that is located in ano ...
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AT&T 555-600-736 - page 22
-20 - When an Off-Premises telephone is connected to the LEGEND system via the 008 OPT module certain accessories must be used for grounding and protecting the system from power surges, electromagnetic interferences, and electrostatic discharges. These components are specified in Section 5 of the LEGEND System Reference Manual. Service technicians ...
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AT&T 555-600-736 - page 23
-21- T-1 (DS1) SERVICE OVERVIEW AND OPERATIONS The goal of the T-1 (DS1) section is to present basic information about T- 1 networking, what it is, how it operates, and what it means to the customer. The section does not explain how the MERLIN LEGEND Communications System interfaces with ISDN-PRI. Further, this Note does not cover the indepth detai ...
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AT&T 555-600-736 - page 24
-22- service, quickly and efficiently. In the past it was necessary to establish a new circuit for virtually every application a customer wished to use. Whether it was teleconferencing, facsimile, hifi audio, video, or computer transmissions, generally a new line or trunk had to be run. It required a lot of time (perhaps months) and money to instal ...
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AT&T 555-600-736 - page 25
-23- The technology for T-1 is moving rapidly. The encoding system and components are not always upgradable to the newer innovations. ● If the customer application requires maximum network reliability, automatic dialing back-up in case of digital facility failure could prove costly. Do GBS Customers Need T-1? Consider this: a standard T-1 circuit ...
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AT&T 555-600-736 - page 26
-24- CHANNEL SERVICE UNIT (CSU) The Channel Service Unit (CSU) provides the interface between the 100D module and the DS1 facilities. T WO AT&T models are available for use on the Legend system: the ESF T1 CSU and the 551 T1 L1 CSU. ● Model 551-T1L1 Reg. Number G1 47226819-/DE-N The 551 T1 CSU is a full-duplex modem, provides data terminal eq ...
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AT&T 555-600-736 - page 27
-25- MULTIPLEXER (MUX) Multiplexer are devices that combine several individual information-carrying channels for transmission over an aggregate link. This is done by allotting this aggregate link to multiple users, in turn to constitute different intermittent channels or time slots (time division multiplexing for digital transport.) A Multiplexer i ...
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AT&T 555-600-736 - page 28
-26- The following table identities the AT&T DS1 services available to customers. DS1 FACILITY SERVICES Digital Signal 1 Service Description ISDN T-1 Megacom (Megacom An outgoing x x WATS) Service domestic long- distance service used in place of WATS service. Megacom 800 Service An incoming, x x domestic toil-free, number service for voice call ...
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AT&T 555-600-736 - page 29
-27- Digital Signal 1 Service Description ISDN T-1 Multiquest Service An incoming 900 x With DNIS number that provides callers with voice and data information service on an interactive basis. software Defined A virtual private x x Network (SDN) networking service Service for voice and circuit switched data calls (Up to 56 Kbps). SDN lets businesses ...
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AT&T 555-600-736 - page 30
-28- Digital Signal 1 Service Station Number Identification/ Automatic Number Identification (SID/ANI) Service Description A caller identification service for systems with display telephones, call report systems, etc. ** SID allows the called station t o display the station number of the caller. ** ANI allows the called station t o display the bill ...
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AT&T 555-600-736 - page 31
-29- SPECIAL HOTEL/MOTEL TRUNKS OPERATION OVERVIEW In certain areas of the country there are special trunks for hotels and motels about which you should be aware. At one time they were widely used but today they are found generally in rural areas. The trunks generally are called HOBIC lines by telephone company personnel. The acronym stands for Hot ...
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AT&T 555-600-736 - page 32
-30- HARDWARE The Legend system hardware most directly connected with Lines/Trunks are the Control Unit Modules. The specifications for each module are presented later in this section. Also the system uses different types of lines/trunks for the different individual functions of each operating mode. In PBX mode the system can use the following: ● ...
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AT&T 555-600-736 - page 33
-31- LEGEND SYSTEM CONTROL UNIT MODULES MODULE 008 008 MLX LINE/TRUNK TYPE n/a n/a 008 OPT n/a STATION TYPE Analog multiline telephone; Call Management System; analog data with a general purpose adapter MLX telephone; digital data service (the ISDN 7500B Data Module) on-premises or off- premises single-line telephone SPECIFICATIONS Capacity: 8 anal ...
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AT&T 555-600-736 - page 34
- 32 - MODULE 012 (T/R) 100D DSI 400/TTR* 400 E&M 400 GS/LS/TTR LINE/TRUNK TYPE n/a T-1 or PRI Loop-start and TTR Tie trunk Loop-start or ground-start and STATION TYPE Single-line telephone; MERLIN attendant; MERLIN MAIL Voice Messaging System T/R adjunct (such as an answering machine or fax machine); analog data device (such as a modem) n/a Po ...
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AT&T 555-600-736 - page 35
-33 - MODULE LINE/TRUNK STATION TYPE SPECIFICATIONS TYPE 408* L00p-start Analog multiline Capacity: 4 lines/trunks, 8 stations. telephone; Call IPFT telephone Management System; Station signaling: analog multiline PFT telephone telephone (40 kbps) Line/trunk signaling: Loop-start line/ trunk: analog voice Loop range: 1000 ft.. in-building and in-ra ...
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AT&T 555-600-736 - page 36
-34- This section lists the LEGEND system trunk and off-premises modules and the appropriate PEC and Comcodes. More complete code information can be found in Section A of the Systems Manual (555 -610- 200). Line/Station Modules PEC Comcode 100D DS1 module 61491 105461560 400 E&M module 400 GS/LS/TTR module 400 (TTR) 408 LS ATL module 408 GS/LS ...
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AT&T 555-600-736 - page 37
-35- ADMINISTRATION To properly administer a MERLIN LEGEND system at the time of initialization requires that care be taken during the planning phase of the sales activity. This is especially true if the system is to connect to a number of different trunks and lines, such as DID, Tie, or ISDN. in addition to using local CO Loop-start and Ground-sta ...
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AT&T 555-600-736 - page 38
-36- REFERENCES GBS SCAN Competitive Newsletter, “Everything You Need to Know About ISDN”, Nov/Dec 1988. MERLIN LEGEND Key System Planning Manual (555-610-112) MERLIN LEGEND PBX System Planning Manual (555-610-113) MERLIN LEGEND Data Guide (555-610- 114), Chapter 2 MERLIN LEGEND System Reference Manual (555-610-110) MERLIN LEGEND Installation, ...
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