KSU-less system

Last updated

A KSU-less telephone system is a type of electronic key telephone system that puts the switching circuitry inside of each individual phone. [1] This eliminates the need for a key service unit (KSU), which in traditional key systems is a centralized cabinet that contains the switching circuitry, and allows phones to be wired together in series while retaining certain advanced key system features such as intercom, paging, and hold. Unlike traditional key systems, however, KSU-less systems support a limited number of extensions and trunk lines and are typically not very scalable. [2] The first KSU-less systems were introduced in the 1970s by the AT&T Corporation.

Contents

History

In traditional key telephone systems, the key service unit (KSU) is a centralized cabinet containing the electronics that handle all of the switching of calls, with each phone connecting to the KSU with its own cable in a star topology. In KSU-less systems, the electronic circuitry is located inside each phone in the system, and the phones are wired in series, as is typical in standard in-wall installations. [3] The advent of large-scale integrated circuits in the mid-1970s made the incorporation of such switching circuitry inside of the phone itself possible, [4] and the first KSU-less system was introduced in 1975 with the Com Key 416 by the AT&T Corporation. [5] [6] The Com Key 416 differed from more modern KSU-less systems, in that the switching circuitry was located only within one phone, designated the master. One master phone supported two phone lines and eight extensions; two masters can be hooked together to support four phone lines and sixteen extensions. As with contemporaneous key system units, the switching circuitry inside the Com Key 416 still contained electromechanical components. [7] With the progression of VLSI technology, newer KSU-less systems were designed with the ICs handling the switching located inside each phone in the system. This eliminated the need for a master phone and increased the reliability of the system. [4]

Wiring

Because of the in-series wiring scheme of most KSU-less systems, installation is typically easier than systems using a key service unit, and standard in-wall installations may be used. [8] [3] Unlike KSU systems or standard POTS lines, KSU-less systems typically require an external power supply unit for each extension. [8] Some KSU-less units sacrifice a trunk to transmit power to each extension on the line, eliminating the need for external PSUs while reducing the number of connections to central offices. [3] Other systems still have a recharable battery backup allowing phone service to continue in case mains power is lost. [9]

Because of their limited amount of trunk connections and extensions, KSU-less systems are not as scalable and are mainly marketed at the small office/home office segment. [2] A basic KSU-less system in the 1990s supported up to three lines and eight extensions, although some more advanced units supported up to four lines and sixteen extensions, [8] and by the early 2000s units were available supporting up to 24 extensions. More advanced KSU-less units may also support a "non-square" topology, in which a private trunk line that cannot be accessed from all extensions can be wired up to only one phone. [3]

Features

The advanced features of KSU-less systems, such as intercom, paging, hold, and transfer, are able to function on the same wire as normal phone service because the switching circuitry moves the inter-office voice path, as well as the signaling necessary to establish such paths, to the high-frequency RF band. Concurrent intercoms are typically not possible on basic KSU-less systems; some advanced systems support up to two simultaneous intercoms. KSU-less systems before the late 1990s typically shared the voicemail between all phones, presenting a potential privacy issue. With the advent of affordable flash storage in the turn of the millennium, KSU-less systems began supporting per-extension voicemail, as well as auto attendants, which presents outside callers with a prerecorded voice menu to dial specific extensions. [3] Due to incompatible signaling schemes, different vendor's KSU-less phones typically cannot be mixed together in the same system. [10]

Related Research Articles

<span class="mw-page-title-main">Telephone switchboard</span> Device used to connect telephone circuits to establish calls between users

A telephone switchboard was a device used to connect circuits of telephones to establish telephone calls between users or other switchboards throughout the 20th century. The switchboard was an essential component of a manual telephone exchange, and was operated by switchboard operators who used electrical cords or switches to establish the connections.

<span class="mw-page-title-main">5ESS Switching System</span>

The 5ESS Switching System is a Class 5 telephone electronic switching system developed by Western Electric for the American Telephone and Telegraph Company (AT&T) and the Bell System in the United States. It came into service in 1982 and the last unit was produced in 2003.

Telephony is the field of technology involving the development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties. The history of telephony is intimately linked to the invention and development of the telephone.

<span class="mw-page-title-main">Blue box</span> Device for hacking telephone networks

A blue box is an electronic device that produces tones used to generate the in-band signaling tones formerly used within the North American long-distance telephone network to send line status and called number information over voice circuits. During that period, charges associated with long-distance calling were commonplace and could be significant, depending on the time, duration and destination of the call. A blue box device allowed for circumventing these charges by enabling an illicit user, referred to as a "phreaker" to place long-distance calls, without using the network's user facilities, that would be billed to another number or dismissed entirely by the telecom company's billing system as an incomplete call. A number of similar "color boxes" were also created to control other aspects of the phone network.

<span class="mw-page-title-main">Demarcation point</span> Boundary of a private and public network

In telephony, the demarcation point is the point at which the public switched telephone network ends and connects with the customer's on-premises wiring. It is the dividing line which determines who is responsible for installation and maintenance of wiring and equipment—customer/subscriber, or telephone company/provider. The demarcation point varies between countries and has changed over time.

<span class="mw-page-title-main">Telephone call</span> Connection between two or more people over a telephone network

A telephone call or telephone conversation, also known as a phone call or voice call, is a connection over a telephone network between the called party and the calling party. Telephone calls started in the late 19th century. As technology has improved, a majority of telephone calls are made over a cellular network through mobile phones or over the internet with Voice over IP. Telephone calls are typically used for real-time conversation between two or more parties, especially when the parties cannot meet in person.

<span class="mw-page-title-main">Business telephone system</span> Telephone system typically used in business environments

A business telephone system is a telephone system typically used in business environments, encompassing the range of technology from the key telephone system (KTS) to the private branch exchange (PBX).

<span class="mw-page-title-main">DMS-100</span> Nortel telecom switch

The DMS-100 is a member of the Digital Multiplex System (DMS) product line of telephone exchange switches manufactured by Northern Telecom. Designed during the 1970s and released in 1979, it can control 100,000 telephone lines.

<span class="mw-page-title-main">Intercom</span> Voice communications system for use within a local area

An intercom, also called an intercommunication device, intercommunicator, or interphone, is a stand-alone voice communications system for use within a building, small collection of buildings or portably within a small coverage area, which functions independently of the public telephone network. Intercoms are generally mounted permanently in buildings and vehicles, but can also be detachable and portable. Intercoms can incorporate connections to public address loudspeaker systems, walkie talkies, telephones, and other intercom systems. Some intercom systems incorporate control of devices such as signal lights and door latches.

<span class="mw-page-title-main">Nortel Meridian</span>

Nortel Meridian is a private branch exchange telephone switching system. It provides advanced voice features, data connectivity, LAN communications, computer telephony integration (CTI), and information services for communication applications ranging from 60 to 80,000 lines.

The BT Versatility is a telephone PBX switchboard sold by BT and targeted at small businesses. It is manufactured by Taratel Communications previously Lake Communications in Ireland as the OfficeLink. In South Africa it was sold by Tellumat as the Convergence 30 or C30, in Australia it was sold as the Commander Connect, in the USA it was sold by Inter-tel as the Encore CX and by Mitel as the Mitel 3000

In residential telephony, an extension telephone is an additional telephone wired to the same telephone line as another. In middle 20th century telephone jargon, the first telephone on a line was a "Main Station" and subsequent ones "Extensions" or even called as intercom. Such extension phones allow making or receiving calls in different rooms, for example in a home, but any incoming call would ring all extensions and any one extension being in use would cause the line to be busy for all users. Some telephones intended for use as extensions have built-in intercom features; a key telephone system for a small business may offer two to five lines, lamps indicating lines already in use, the ability to place calls on 'hold' and an intercom on each of the multiple extensions.

<span class="mw-page-title-main">AT&T Merlin</span> Corporate telephone system

AT&T Merlin is a corporate telephone system by American Telephone and Telegraph (AT&T) that was introduced in late 1983, when it was branded American Bell Merlin. After the breakup of AT&T in 1984, it was rebranded and later also supplied by Lucent and Avaya.

<span class="mw-page-title-main">1A2 Key Telephone System</span> Modular business telephone system

The 1A2 Key Telephone System is a business telephone system developed and distributed by the Western Electric Company for the Bell System.

The Number Five Crossbar Switching System is a telephone switch for telephone exchanges designed by Bell Labs and manufactured by Western Electric starting in 1947. It was used in the Bell System principally as a Class 5 telephone switch in the public switched telephone network (PSTN) until the early 1990s, when it was replaced with electronic switching systems. Variants were used as combined Class 4 and Class 5 systems in rural areas, and as a TWX switch.

<span class="mw-page-title-main">Microsoft Response Point</span>

Microsoft Response Point was an advanced software-based telephone system developed by Microsoft. Response Point, a PBX system targeting small businesses with less than 50 employees, was launched in March 2007, with systems available on the market in the fourth quarter of that year. Response Point is VoIP-based, and uses SIP as its signaling and call setup protocol. Response Point supports voicemail and multi-party calling in addition to two party VoIP calls. Response Point features innovative voice recognition technology to manage calls and voice mail. Voicemail messages can, optionally, be sent to e-mail where they can be retrieved and archived. Response Point voice dialing can work with the Response Point phone directory which is currently limited to 1100 contacts per user. Contacts may be imported from the Windows Address Book or Microsoft Outlook. Response Point automatically detects gateways and phones connected to the network.

<span class="mw-page-title-main">British telephone socket</span> Type of telephone socket design

British telephone sockets were introduced in their current plug and socket form on 19 November 1981 by British Telecom to allow subscribers to connect their own telephones. The connectors are specified in British Standard BS 6312. Electrical characteristics of the telephone interface are specified by individual network operators, e.g. in British Telecom's SIN 351. Electrical characteristics required of British telephones used to be specified in BS 6305.

<span class="mw-page-title-main">Modem</span> Device that modulates an analog carrier signal to encode digital information

A modulator-demodulator or most commonly referred to as modem is a computer hardware device that converts data from a digital format into a format suitable for an analog transmission medium such as telephone or radio. A modem transmits data by modulating one or more carrier wave signals to encode digital information, while the receiver demodulates the signal to recreate the original digital information. The goal is to produce a signal that can be transmitted easily and decoded reliably. Modems can be used with almost any means of transmitting analog signals, from light-emitting diodes to radio.

Ringing is a telecommunication signal that causes a bell or other device to alert a telephone subscriber to an incoming telephone call. Historically, this entailed sending a high-voltage alternating current over the telephone line to a customer station which contained an electromagnetic bell. It is therefore also commonly referred to as power ringing, to distinguish it from another signal, audible ringing, or ringing tone, which is sent to the originating caller to indicate that the destination telephone is in fact ringing.

<span class="mw-page-title-main">Telephone exchange</span> Interconnects telephones for calls

A telephone exchange, also known as a telephone switch or central office, is a crucial component in the public switched telephone network (PSTN) or large enterprise telecommunications systems. It facilitates the interconnection of telephone subscriber lines or digital system virtual circuits, enabling telephone calls between subscribers.

References

  1. ↑ Main, Max (2003). HTI+. Que. pp. 165, 169. ISBN   9780789729378 – via Google Books.
  2. 1 2 Peterson, Kerstin (2000). Business Telecom Systems: A Guide to Choosing the Best Technologies and Services. CRC Press. pp. 80–81. ISBN   9781482294569 – via Google Books.
  3. 1 2 3 4 5 Green, Andy (May 2001). "Keeping it Simple with KSU-less". Teleconnect. 19 (5). UBM LLC: 52. Archived from the original on January 11, 2002.
  4. 1 2 Klein, Jack (December 1990). "Another Solution: Today's KSUless Technology Can Benefit Your Centrex Service". Teleconnect. 8 (12). UBM LLC: 87 – via Gale.
  5. ↑ Marcus, Michael N. (June 1995). "KSU-less Key System Update". Teleconnect. 13 (6). UBM LLC: 117 et seq. – via Gale.
  6. ↑ Gundlach, Richard (December 11, 1975). "Telephones at 100: Transformed by technology for new functions". Electronics. 48 (25). McGraw-Hill: 90–100 – via the Internet Archive.
  7. ↑ Newton, Harry (1994). Which Phone System Should I Buy?. Flatiron Publishing. p. 7-2. ISBN   9780936648590 – via the Internet Archive.
  8. 1 2 3 The Essential Business Buyer's Guide. Sourcebooks. 1997. p. 201. ISBN   9781570711305 – via the Internet Archive.
  9. ↑ Brooks, Matthew (October 1995). "Telecommunications for the home office". Managing Office Technology. 40 (10). OfficeVision: 8 – via Gale.
  10. ↑ Jainschigg, John B. (March 1996). "Bye-bye busy signal". Home Office Computing. 14 (3). Line56: 94 et seq. – via Gale.
This page is based on this Wikipedia article
Text is available under the CC BY-SA 4.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.