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60-705: The purpose of the DMS-100 Switch is to provide local service and connections to the PSTN public telephone network. It is designed to deliver services over subscribers' telephone lines and trunks . It provides plain old telephone service (POTS), mobility management for cellular phone systems, sophisticated business services such as automatic call distribution (ACD), Integrated Services Digital Network (ISDN), and Meridian Digital Centrex (MDC), formerly called Integrated Business Network (IBN). It also provides Intelligent Network functions (AIN, CS1-R, ETSI INAP ). It

120-406: A timeslot because DS0s are aggregated in time-division multiplexing (TDM) equipment to form higher capacity communication links. A Digital Signal 1 (DS1) circuit carries 24 DS0s on a North American or Japanese T-carrier (T1) line, or 32 DS0s (30 for calls plus two for framing and signaling) on an E-carrier (E1) line used in most other countries. In modern networks, the multiplexing function

180-732: A Central Terminal (CT) that had the dial tone lines wired into it and a remote box called a Remote terminal (RT) where the dial tone 'came out'. They used 2-6 T1 links on copper - i.e. LD-1 or fiber. As telcos modernized, these remote boxes were re-configured to work directly from a SMU peripheral at the host DMS. Typically each SMU can handle 3-6 RCUs. Transmitters, receivers and other service circuits are in Trunk Module (TM) and Miscellaneous Trunk Module (MTM) shelves. Trunks are on DTC (Digital Trunk Controller) or DTCI (Digital Trunk Controller ISDN) or PDTC (PCM30 Digital Trunk Controller) shelves, usually two T-1 lines per card, ten cards per DTC for

240-586: A DISKUT command line program. Analog lines are terminated on individual line cards , each with its own codec , in pull-out Line Drawers in frames. The original design of such frames was called the Line Module (LM) with 32 lines per drawer. LMs were not able to send caller-id information (CLASS services) and became rare late in the century, having been supplemented or replaced by the newer Line Concentrating Module (LCM). Duplicated ringing generators serve each LM or pair of LCM. For DC testing, each line card has

300-478: A Line Group Controller (LGC) and communicate over DS-30 connections to NT6X48AA interface cards on the LGC. The number of LCMs per LGC depends on traffic: 3-4 LCM per LGC but as few as two where traffic is heavy. Remote offices, anywhere from a kilometre to 100 km from the host, can be served by a Remote Line control Module (RLCM), Remote Switching Center (RSC); a later vintage is known as RCC2. They use T1 links to

360-546: A Message Controller. The Compute Module contains redundant SuperNode CPUs to handle call processing and maintenance functions and, like the NT40 core, can operate in a synchronized mode with its mate. The System Load Module contains all the necessary software for every element of the DMS switch and also provides file system and data storage functions on magnetic tape and hard disk. The Message Controller provides communications links between

420-653: A benchmark for the development of the Telecommunications Industry Association 's TIA-TSB-116 standard on voice-quality recommendations for IP telephony, to determine acceptable levels of audio latency and echo. In most countries, the government has a regulatory agency dedicated to provisioning of PSTN services. The agency regulate technical standards, legal requirements, and set service tasks may be for example to ensure that end customers are not over-charged for services where monopolies may exist. These regulatory agencies may also regulate

480-657: A descriptor out of bounds or indexing a NULL descriptor will cause a descriptor range check trap. UPB is generally used by application software to more gracefully handle index out of range. Note NULL can be used for pointers and descriptors. Strings use descriptors extensively. Strings are of a defined length with no NULL character terminator. Block scope is defined by BLOCK and ENDBLOCK statements, which are analogous to BEGIN END in Pascal or { } in C. Blocks can optionally be labeled for enhanced compiler checking and functionality. Procedures and functions are only differentiated by

540-528: A distributed architecture allowing for the development of new features and services. Each of the elements of the DMS SuperNode uses a common SuperNode CPU hardware design differing only in the software used to control them. The SuperNode consists of two main elements: DMS Core and DMS Bus. DMS Core provides the main computing facility and is made up of the Compute Module, System Load Module and

600-418: A load; if AREAs were planned smartly, this would not affect the placement of modules in memory, thereby avoiding a restart. A SECTION is a text file containing source code and directives to manage the different section types and their position in the module hierarchy. A SECTION is the smallest unit of compilation. A MODULE is the smallest unit of linkage and loading and contains one or more sections. A SUBSYSTEM

660-495: A mate exchange bus (MEB) between the two CPUs enables the state of one CPU to be continuously compared to that of the other CPU on a cycle by cycle basis. Any discrepancy between the two CPUs results in maintenance circuitry determining which CPU is at fault and activity to change to the same CPU. A Program Store is dedicated to each CPU and is a memory for the program instructions required by that CPU for processing calls, maintenance and for administrative tasks. The PS associated with

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720-569: A network of fixed-line analog telephone systems, the PSTN is almost entirely digital in its core network and includes mobile and wireless networks, all of which are currently transitioning to use the Internet Protocol to carry their PSTN traffic. The technical operation of the PSTN adheres to the standards internationally promulgated by the ITU-T . These standards have their origins in

780-478: A relay to connect it to a test bus. LCM have smaller line cards, serving 64 lines per physical drawer (two logical drawers) of the same size as in the LM. An LCM requires only half the space as an LM for the same number of lines. The majority of line cards are NT6X17, with three relays for loop start lines. Others include NT6X18 which have four or more relays and a slide switch for ground start lines (a newer version of

840-452: A safe way. Protected data survives all restarts short of a system image reload. Note WRITE_PROTECTED_STORE arguments are type agnostic as long as the types of both arguments match. PRIVATE provides a private copy of the data for each process that uses it. There is no COW functionality, each process is allocated its own copy and optionally initializes it at creation. Note Local variables defined using DECL are naturally private. Gazinta

900-403: A total of 480 DS-0 voice channels. At the turn of the century many original NT6X50AA cards were still in service that cannot perform T-carrier extended superframe signaling, this can be performed with a plug-in replacement NT6X50AB card, used for services such as PBX ISDN T1s. Trunks can also be provisioned on SPM (Synchronous Peripheral Module) capable of handling 2016 DS0s, nearly 4.2x more than

960-415: Is @ and is placed after the ptr. A NULL pointer is a predefined value that is guaranteed not to point to a mapped address. It is not 0 nor -1 nor another the predefined uninitialized memory pattern (#FDFD). In other words, a pointer is not NULL by default, it must be set in the code. Pointer arithmetic is not supported. Note Dereferencing a NULL pointer will cause a data access trap. The descriptor 'DESC'

1020-478: Is a compiler defined structure containing a pointer to an array and the array upperbound. A descriptorized array is indexed using simple array syntax 'MY_DESC[I]' and the UPB operator can be used to access the upperbound 'UPB MYDESC'. A TDSIZE operator also exists as a legacy of the descriptor implementation on NT40: TDSIZE = UPB+1. Descriptors have automatic run time bounds checking on dynamically allocated arrays. Indexing

1080-415: Is known as Remote Carrier Urban (RCU). Such units typically reside on the side of a road in a large box, approx 3 meters across, almost 2 meters high and almost a meter through. In the 1980s many telcos installed an early version of these instead of pulling more cable into a remote area. They were much cheaper and could provide up to approx 500 lines. Back then they needed two 'boxes' to work- a host box called

1140-488: Is moved as close to the end user as possible, usually into cabinets at the roadside in residential areas, or into large business premises. These aggregated circuits are conveyed from the initial multiplexer to the exchange over a set of equipment collectively known as the access network . The access network and inter-exchange transport use synchronous optical transmission, for example, SONET and Synchronous Digital Hierarchy (SDH) technologies, although some parts still use

1200-637: Is now defunct. PSTN The public switched telephone network ( PSTN ) is the aggregate of the world's telephone networks that are operated by national, regional, or local telephony operators. It provides infrastructure and services for public telephony . The PSTN consists of telephone lines , fiber-optic cables , microwave transmission links, cellular networks , communications satellites , and undersea telephone cables interconnected by switching centers , such as central offices , network tandems , and international gateways, which allow telephone users to communicate with each other. Originally

1260-794: Is performed in E-Net, similar to the Communication Module of 5ESS switch or the Switching Network of EWSD or the Group Switch of AXE telephone exchange . There are also DMS-200 and DMS-250 variants for tandem switches. In 2006 Nortel introduced the Communication Server 1500 (CS 1500) Softswitch based on VOIP to modernize the DMS-based telephone switches. A CS 1500 softswitch system can replace all

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1320-399: Is switched using a call set up protocol (usually ISUP ) between the telephone exchanges under an overall routing strategy . The call is carried over the PSTN using a 64 kbit/s channel, originally designed by Bell Labs . The name given to this channel is Digital Signal 0 (DS0). The DS0 circuit is the basic granularity of circuit switching in a telephone exchange. A DS0 is also known as

1380-447: Is the basic union structure. It is declared and used in a manner similar to Pascal-descended languages. Areas are memory blocks that could be cast to TABLES and OVERLAYS. They are declared in bytes and typically are declared large enough to allow for future expansion. This is due to the desire to upgrade DMS software 'live' without requiring a restart. The modular nature of PROTEL allows relatively small chunks of code to be swapped into

1440-412: Is the colloquial name used for the assignment operator '->'. Its name comes from 'goes into' meaning expression gazinta (goes into) variable. Expressions are evaluated in strict left to right order with no operator precedence. Lack of operator precedence is a legacy of the NT40 processor which used a stack based ALU using RPN logic. Parentheses are used to prioritize subexpressions. The pointer operator

1500-484: Is used for reserved words. Most global and all local variables are declared using the DECL reserved word. Variables can be initialized using INIT keyword. Constants use IS keyword, hexadecimal uses #. Global variables can also use PROTECTED, or PRIVATE declarations to define write protected data or thread local data respectively. Writes to protected data requires the use of builtin primitives that alter protected data in

1560-565: Is used in countries throughout the world. There are also DMS-200 and DMS-250 variants for tandem switches. Much of the hardware used in the DMS-100, with the possible exception of the line cards, is used in other members of the DMS family, including the DMS-200 toll switch. All power distribution is at -48 VDC (nominal), from which DC to DC converters on every shelf provide other necessary voltages. The Central Control Complex comprises

1620-622: The Broadband Integrated Services Digital Network (B-ISDN). The B-ISDN vision was overtaken by the disruptive technology of the Internet . At the turn of the 21st century, the oldest parts of the telephone network still used analog baseband technology to deliver audio-frequency connectivity over the last mile to the end-user. However, digital technologies such as DSL , ISDN , FTTx , and cable modems were progressively deployed in this portion of

1680-519: The DMS-100 . Protel-2 is the object-oriented version of Protel. The PROTEL language was designed to meet the needs of digital telephony and is the basis of the DMS-100 line of switching systems. PROTEL is a strongly typed, block-structured language which is based heavily on PASCAL and ALGOL 68 with left-to-right style of variable assignment, variable-sized arrays, and extensible structures. The designers of PROTEL significantly extended PASCAL of

1740-421: The last mile from the exchange to the telephone in the home (also called the local loop ). To carry a typical phone call from a calling party to a called party , the analog audio signal is digitized at an 8 kHz sample rate with 8-bit resolution using a special type of nonlinear pulse-code modulation known as G.711 . The call is then transmitted from one end to another via telephone exchanges. The call

1800-485: The 1970s, the telecommunications industry began implementing packet-switched network data services using the X.25 protocol transported over much of the end-to-end equipment as was already in use in the PSTN. These became known as public data networks , or public switched data networks. In the 1980s, the industry began planning for digital services assuming they would follow much the same pattern as voice services and conceived end-to-end circuit-switched services, known as

1860-738: The Central Processing Unit (CPU), Program Store (PS), Data Store (DS) and the Central Message Controller (CMC). The CPU contains two identical 16-bit processors running in hot standby mode. The original CPU core was referred to as the NT40 CPU and was implemented in approximately 250 discrete logic devices across several circuit boards running at 36 MHz. The NT40 core consisted mainly of the NT1X44 stack card, which provides some register and stack functions of

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1920-700: The DMS Core and the DMS Bus. DMS Bus is used to interconnect the DMS Core, the switching network and the Input/Output controller (IOC) and manage message flows between these units and consists of redundant Message Switches. The Message Switches of the DMS Bus operate in a load-sharing mode and one of them provides the main clock source for the DMS-100 system while the others are synchronized to it. Messages between all SuperNode units are carried by optical DS512 links. The operating system used by both generations of

1980-688: The DMS component modules except for the LCMs, reducing the footprint of a DMS-100 to one 19" rack and allowing operators to reduce cooling and power requirements significantly. A successor to the DMS-100 is the Communication Server 2000 (CS2K), which shares many components and software with the DMS. The significant difference is the addition of VOIP technology into the CS2K. In 2010, Genband purchased Nortel Networks' Carrier VoIP and Application Solutions (CVAS) business for $ 182.5 million. Nortel

2040-504: The DMS-100 switch was called Support Operating System (SOS) and was written in a high level language called PROTEL which stood for PRocedure Oriented Type Enforcing Language developed at Bell Northern Research (BNR). Hardware and maintenance are administered locally through cathode-ray terminals, through a multilevel menu system called MAPCI. There are various methods used to access the DMS remotely as well, including modem and telnet. Backups and other hard drive work are administered through

2100-606: The DTC. Internal connections to the time switch (network) are on 2.56 Mbit/s (DS-30) Speech Links, each carrying thirty channels plus synchronization and data channels, on four wires plus a ground wire. Connections to the network are handled by the NT6X40AA DS-30 interface card on an LGC or LTC and these link may also be DS-512 optical interfaces. Using the NT6X44AA time switch card, LGCs and LTCs internally map channels on

2160-678: The Motorola 68030 . In the early 1990s it was further upgraded to use the Motorola 88100 and 88110 Reduced Instruction Set Computing (RISC) CPUs. This RISC version of the SuperNode Computing Module was known as the BRISC (BNR Reduced Instruction Set Computing) CPU. With the BRISC CPU the DMS SuperNode had a processing capacity of 1,500,000 call attempts per hour. DMS SuperNode featured increased processing capacity across

2220-622: The NT6X18 has eliminated the ground switch). The NT6X18 also has the ability to provide current reversal required for some coin phones and business systems. The NT6X17B and the NT6X18B is known as the world line card and is software configurable to more than 15 million functional settings to meet almost any signalling and transmission requirement in any market. NT6X19 line cards allow the use of older style, neon message-waiting lamps, this feature also requires an additional card per drawer that supplies

2280-524: The NT6X48AA DS-30 & NT6X50AA/AB DS1 interface links to available channels on NT6X40AA DS-30 or NT6X40FA DS-512 interfaces out to the network. European PDTCs were complemented by the DTCOI2 and DTCO2. The DTCOI2 was designed to run PRI and DPNSS services as per existing PDTCOI and MSB7 peripherals. The DTCO2 was designed to carry CAS and SS7 as per existing PDTCO peripheral. Time Division switching

2340-641: The Network Message Controller (NMC) in the various Network Modules (NM), or the Input/Output Controller (IOC). Both CPUs have access to either CMC which share the message load to the Line Modules or peripherals. The original NT40 based CCC was replaced by the compatible DMS SuperNode in 1987. The DMS SuperNode Computing Module was first based on the Motorola 68020 Central Processing Unit (CPU) and then upgraded to

2400-567: The PSTN evolved over time to support an increasing number of subscribers, call volume, destinations, features, and technologies. The principles developed in North America and in Europe were adopted by other nations, with adaptations for local markets. A key concept was that the telephone exchanges are arranged into hierarchies, so that if a call cannot be handled in a local cluster, it is passed to one higher up for onward routing. This reduced

2460-480: The PSTN, usually for military purposes. There are also private networks run by large companies that are linked to the PSTN only through limited gateways , such as a large private branch exchange (PBX). The task of building the networks and selling services to customers fell to the network operators . The first company to be incorporated to provide PSTN services was the Bell Telephone Company in

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2520-715: The United States. In some countries, however, the job of providing telephone networks fell to government as the investment required was very large and the provision of telephone service was increasingly becoming an essential public utility . For example, the General Post Office in the United Kingdom brought together a number of private companies to form a single nationalized company . In more recent decades, these state monopolies were broken up or sold off through privatization . The architecture of

2580-459: The core. The NT1X48 processor maintenance card contained a thumbwheel on the faceplate to enable various diagnostic tests of the CPU. A later modification of these same five circuit boards with faster pin-compatible discrete logic devices enabled the CPU to operate at 40 MHz allowing central offices to improve call throughput capacity by 10 percent. When the CPU is configured in dual hot standby mode,

2640-467: The day by adding external compilation and extending the data structures available in the language. The PROTEL compiler is tightly integrated with the operating system (SOS), application (CALLP), the development environment (PLS) and originally the processor (NT40). PLS, SOS, CALLP and the compiler itself are all written in PROTEL. Any description of the PROTEL language can't help but include some aspects of

2700-472: The development of local telephone networks, primarily in the Bell System in the United States and in the networks of European ITU members. The E.164 standard provides a single global address space in the form of telephone numbers . The combination of the interconnected networks and a global telephone numbering plan allows telephones around the world to connect with each other. Commercialization of

2760-399: The end of the 20th century. The growth of the PSTN was enabled by teletraffic engineering techniques to deliver quality of service (QoS) in the network. The work of A. K. Erlang established the mathematical foundations of methods required to determine the capacity requirements and configuration of equipment and the number of personnel required to deliver a specific level of service. In

2820-412: The exchange principle already employed in telegraph networks. Each telephone was wired to a telephone exchange established for a town or area. For communication outside this exchange area, trunks were installed between exchanges. Networks were designed in a hierarchical manner until they spanned cities, states, and international distances. Automation introduced pulse dialing between the telephone and

2880-521: The exchange so that each subscriber could directly dial another subscriber connected to the same exchange, but long-distance calling across multiple exchanges required manual switching by operators. Later, more sophisticated address signaling, including multi-frequency signaling methods, enabled direct-dialed long-distance calls by subscribers, culminating in the Signalling System 7 (SS7) network that controlled calls between most exchanges by

2940-465: The host LGC. RCCs/RCC2s work like LTCs in controlling LCMs. Large remotes may have 2+ RCC/RCCs and they can be equipped with links between the RCCs - Interlinks; so calls within the remote do not tie up host links. The RCCs/RCC2s are usually equipped so they will provide calling within the remote office if the host links fail; this feature is called ESA; Emergency Stand Alone . Another type of remote office

3000-569: The interface to end-users remaining the same. Several other European countries, including Estonia, Germany, Iceland, the Netherlands, Spain and Portugal, have also retired, or are planning to retire, their PSTN networks. Countries in other continents are also performing similar transitions. Protel Protel stands for "Procedure Oriented Type Enforcing Language". It is a programming language designed in 1975 by Nortel Networks and used on telecommunications switching systems such as

3060-505: The network, primarily to provide high-speed Internet access. As of 2023 , operators worldwide are in the process of retiring support for both last-mile analog telephony and ISDN, and transitioning voice service to Voice over IP via Internet access delivered either via DSL , cable modems or fiber-to-the-premises , eliminating the expense and complexity of running two separate technology infrastructures for PSTN and Internet access. Several large private telephone networks are not linked to

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3120-415: The number of connecting trunks required between operators over long distances, and also kept local traffic separate. Modern technologies have brought simplifications Most automated telephone exchanges use digital switching rather than mechanical or analog switching. The trunks connecting the exchanges are also digital, called circuits or channels. However analog two-wire circuits are still used to connect

3180-506: The older PDH technology. The access network defines a number of reference points. Most of these are of interest mainly to ISDN but one, the V reference point , is of more general interest. This is the reference point between a primary multiplexer and an exchange. The protocols at this reference point were standardized in ETSI areas as the V5 interface . Voice quality in PSTN networks was used as

3240-453: The other CPU contains identical program instructions. A Data Store is dedicated with each CPU and contains dynamic information on a per-call basis, as well as customer data and office-specific settings. The other CPU is also associated with its own DS containing duplicate data. The Central Message Controller controls the flow of messages between the other units of the CCC and prioritizes them for

3300-409: The other components. PROTEL has very strict type enforcement but the tight coupling of the components creates opportunities to bypass some type checking for skilled coders by using internal compiler features directly. PROTEL is considered 'wordy', containing a large number of reserved words with some statements reading like English. PROTEL source code is case insensitive but by convention upper case

3360-535: The presence of the RETURNS clause and the requirement to include a RETURN statement. A RETURN statement may be inserted anywhere in a function or procedure. Declaration Implementation The TABLE is the basic array structure. TABLE is only used for arrays whose size is known at compile time. Descriptors are the preferred way to reference arrays. Indexing a table out of range will cause a table range check trap. UPB and TDSIZE operators also apply to tables. The OVERLAY

3420-437: The prices charged between the operators to carry each other's traffic . In the United Kingdom, the copper POTS and ISDN-based PSTN is being retired in favour of SIP telephony , with an original completion date of December 2025, although this has now been put back to January 2027. See United Kingdom PSTN switch-off . Voice telephony will continue to follow the E.163 and E.164 standards, as with current mobile telephony, with

3480-562: The processor, the NT1X45 which contained the arithmetic and logic functions, the NT1X46 which provides more registers and the load-route read-only memory (ROM) and the NT1X47 timing and control card which provides the micro-cycle source and microstore decoding functions of the processor. The NT1X47 card also contained the 2-digit hexadecimal display to indicate test result codes and the condition of

3540-502: The telephone began shortly after its invention, with instruments operated in pairs for private use between two locations. Users who wanted to communicate with persons at multiple locations had as many telephones as necessary for the purpose. Alerting another user of the desire to establish a telephone call was accomplished by whistling loudly into the transmitter until the other party heard the alert. Bells were soon added to stations for signaling . Later telephone systems took advantage of

3600-576: The voltage. Type NT6X21 cards serve P-sets (Meridian Business Sets), a special analogue telephone with a proprietary Nortel data link operating at 8 kHz to provide advanced call handling services. For example, a telephone number may appear on multiple P-sets even though each such telephone has only one pair of wires, thus providing a simpler replacement for key telephone systems . An LCME, for ISDN service, which uses NTBX27 cards serve Basic Rate ISDN lines. When provided with ring generators, an LCME can also support other linecard types. LCMs are served by

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