hacking

	==Phrack Inc.==
	Volume One, Issue Three, Phile 9 of 10

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	@ PRIVATE @
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	@ Presents... @
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	@ \\\\\=-{ Knight Lightning's }-=///// @
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	@ "Introduction to PBXs" @
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	@ Written on January 3, 1986 @
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	This file is a personal continuation of the PBX entry in the MCI
	Telecommunications Glossary.
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	A telephone exchange serving an individual organization and having connections
	to a public telephone exchange is called a Private Branch Exchange (PBX). The
	PBX performs a switching function by connecting any extension in the private
	organization to an outside line. A PBX is actually a private switch that
	connects a group of telephones within an individual organization. Calls placed
	outside this individual group are connected to a telephone company's central
	office switch through trunks. A PBX may be operated by an attendant from the
	private organization or the switching system may be done automatically. Other
	terms that are commonly used interchangeably with PBX are: Private Automatic
	Branch Exchange (PABX), Private Automatic Exchange (PAX), and Computerized
	Branch Exchange (CBX). Although these terms were originally used to identify
	specific switch structures, today they are often used as synonyms.

	PBXs can use any of three basic switching methods: step-by-step (SxS),
	Cross-bar (X-bar), and computer controlled, to perform the basic function of
	switching. However, in addition to detecting calls and establishing a
	transmission link between two telephones, PBXs can do much more.

	The common control, often called a central processing unit (CPU), controls the
	switching matrix that connects the stations and trunks. The switching matrix
	of a PBX performs the same job as does an operator at a manual switchboard or a
	common control central office switch. The CPU, however, gets its instructions
	from the "stored program", which contains directions for activities, such as
	detecting calls, sending them over the best available route, and recording
	billing information. These computerized electronic switches are used to
	perform routine, as well as unique, functions that simply weren't practical or
	even possible with electromechanical switches.

	Just as in the public switched network, PBX switches make connection between
	instruments, or "key telephone sets". We're all familiar with key telephone
	sets, whether we know them by name or not. They're the business telephones
	that have six push-button keys lined up below the dial--a red button marked
	"hold" and five buttons or lines with flashing lights.

	Systems with PBXs and key sets have a great deal of flexability in planning for
	their needs because they can set up their codes to accomplish the functions
	needed in their particular situations. In fact, the PBX can be programmed so
	that each individual extension within a system can take advantage of features
	applicable to its own business needs.

	Some of the features that are availiable with PBXs and key systems are: call
	transfer, which allows internal or external calls to be transferred from one
	telephone to any other phone in the system; automatic push-button signaling,
	which indicates the status of all phones in the system with display lights and
	buttons; one-way voice paging, which can be answered by dialing the operator
	from the nearest telephone in the system; camp-on, in which a call made to a
	busy phone automatically waits until the line is idle; and internal and
	external conference capabilities, which enables outside callers to conference
	with several inside users.

	Some features automatically handle incoming telephone calls. Automatic call
	waiting not only holds calls made to a busy extension until the extension is
	free, but also signals the person being called that a call is waiting and
	informs the caller that he is on hold. Automatic call forwarding will send
	calls to employees who are temporarily in locations other than their offices,
	provided they "inform" the PBX where they can be found. Automatic call
	distribution automatically send an incoming call to the first extension that's
	not busy--a useful feature for situations in which any one of a group of
	persons in the organization can adequately respond to incoming calls. Another
	example is automatic call back, which allows a caller who reaches a busy line
	to ask the PBX to return his or her call when the line is free.

	Still other features provide services such as night telelphone answering,
	telephone traffic monitoring, and network or hot-line connection. These
	examples are but a sample from the features possible with computerized PBXs.

	===============================================================================
	This is a very brief description of how to use and what to expect on a PBX.
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	Basically, you call the PBX and you will have to enter a code that can be
	anywhere from 4 to 6 digits (Note: some PBXs do not require codes). Then you
	will hear a dial tone. From here you would under normal circumstances dial:
	9 + 1 (or 0) + NPA-PRE-SUFF, for long distance dialing or dial 8 for local
	dialing.

	The most common use of the PBX is to call Alliance Teleconferencing,
	a teleconference service offered by AT&T. To do this dial:
	0700-456-1000,1002,1003,2000,2001,2002.

	Note: PBX codes are usually very simple and usually 4 digits.
	EX: 0000, 1111, 1234, etc
	===============================================================================
	Look for a file on Alliance Teleconferencing coming soon...
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	This has been a Knight Lightning presentation...

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