81 lines
5.0 KiB
Plaintext
81 lines
5.0 KiB
Plaintext
Computer Based PBX Courtesy of the Jolly Roger
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(Originally an Apple ][ file for forgive the upper case!)
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TO GET A BETTER UNDERSTANDING OF WHAT A PBX CAN DO, HERE ARE A FEW BASIC
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FUNDAMENTALS.THE MODERN PBX IS A COMBINED COMPUTER,MASS STORAGE DEVICE,
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AND OF COURSE A SWITCHING SYSTEM THAT CAN:
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[1] PRODUCE ITEMIZED,AUTOMATED BILLING PROCEDURES,TO ALLOW THE
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IDENTIFICATION AND MANAGEMENT OF TOLL CALLS. [HAHAHA]
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[2] COMBINE DAYTIME VOICE GRADE COMMUNICATION CIRCUITS INTO
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WIDEBAND DATA CHANNELS FOR NIGHT TIME HIGH SPEED DATA
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TRANSFERS.
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[3] HANDLES ELECTRONIC MAIL [ INCLUDING OFFICE MEMOS ].
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[4] COMBINE VOICE CHANNELS INTO A WIDEBAND AUDIO/VISUAL
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CONFERENCE CIRCUIT,WITH THE ABILITY TO XFER AND
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CAPTURE SLIDES,FLIPCHARTS,PICTURES OF ANY KIND.
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BOTH THE EXTERNAL AND INTERNAL CALLING CAPACITY OF THE PBX SYSTEM MUST BE
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CAREFULLY CONSIDERED BECAUSE MANY BUSINESS OPERATIONS RUN A VERY HIGH RATIO
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OF INTERNAL STATION TO STATION DIALING AND A LOW CAPACITY SYSTEM WILL NOT
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HANDLE THE REQUESTED TRAFFIC LOAD.
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A CRITICAL FACTOR IS THE NUMBER OF TRUNKS AND THE CENTRAL OFFICE FACILITIES
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THAT ARE USED FOR OUTSIDE CONNECTIONS.ANOTHER IS THE NUMBER OF JUNCTIONS OR
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[LINKS] THAT MAKE UP THE INTERNAL CALLING PATHS.
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TO UNDERSTAND THE SERVICES AVAILABLE ON A TYPICAL COMPUTER RUN PBX IT IS
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NECESSARY TO INTRODUCE THE SUBJECT OF TIME DIVISION SWITCHING.IN A TIME
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DIVISION SWITCHING NETWORK ALL CONNECTIONS ARE MADE VIA A SINGLE COMMON BUS
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CALLED (OF COURSE) A 'TIME-DIVISION BUS'.EVERY LINE TRUNK THAT REQUIRES A
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CONNECTION WITH ANOTHER IS PROVIDED WITH A PORT CIRCUIT.ALL PORT CIRCUITS
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HAVE ACCESS TO THE TIME DIVISION BUS THROUGH A TIME DIVISION SWITCH.
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[WHEN TWO PORTS REQUKRE CONNECTION,THEIR TIME DIVISION SWITCHES OPERATE AT
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A VERY HIGH FREQUENCY (16,000 TIMES PER SECOND).THIS TECHNIQUE,WHICH IS
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CALLED 'SPEECH SAMPLING',ALLOWS MANY SIMULTANEOUS CONNECTIONS OVER THE SAME
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TIME DIVKSION BUS.EACH CONNECTION IS ASSIGNED A TIME INTERVAL,THE 'TIME SLOT'
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,AND THE NUMBER OF TIME SLOTS IDENTIFIES THE NUMBER OF SIMULTANEOUS CONNECT-
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IONS AMONG PORTS.]
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THE NEXT CRITICAL ITEM IS CIRCUIT PACKS.THE SYSTEM ELEMENTS THAT WE WILL BE
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DESCRIBING IN FUTURE TUTORIALS [LINES/TRUNKS/SWITCHES,MEMORY AND CONTROL] ARE
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CONTAINED ON PLUG IN CIRCUIT PACKS.EACH LINE CIRCUIT PACK CONTAINS A NUMBER
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OF LINES,IN EXAMPLE,FOUR.BUT THE ASSIGNMENT OF STATION NUMBERS TO ACTUAL
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PHONE LINE CIRCUITS IS FLEXIBLE.
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THE SYSTEM MEMORY IS CONTAINED IN CIRCUIT PACKS WHICH PROVIDE THE CALL
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PROCESSING FUNCTIONS.THE CIRCUIT PACKS ARE HELD IN SMALL FRAMES CALLED
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'CARRIERS'.WITHIN EACH CARRIER,THE CIRCUIT PACKS ARE PLUGGED INTO POSITIONS:
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THE 'SLOTS'.EVERY CIRCUIT CAN BE ADDRESSED BY,SAY A FIVE DIGIT NUMBER WHICH
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TELLS ITS LOCATION BY CARRIER-SLOT-CIRCUIT.... [STARTING TO GET THE IDEA?]
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THERE CAN BE THREE TYPES OF CARRIERS IN A MODERN PBX SYSTEM:
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O LINE CARRIERS
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O TRUNK CARRIERS
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O CONTROL CARRIERS
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THE LINE CARRIERS CONTAIN STATION LINES.IN A.T.& T.'S "DIMENSION" MODEL,FOR
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EXAMPLE,A TOTAL OF 52 TO 64 LINES ARE PROVIDED.THE TRUNK CARRIERS CONTAIN
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SLOTS FOR 16 TRUNK CIRCUIT PACKS.THE CONTROL CARRIER INCLUDES PROCESSOR,
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MEMORY,CONTROL CIRCUITRY,DATA CHANNELS FOR ATTENDANT CONSOLE CONTROL AND
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TRAFFIC MEASUREMENT OUTPUTS.
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PBX SYSTEMS WILL DIRECTLY REFLECT THE TYPES OF SERVICES OFFERED AT THE C.O.
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O CCSA
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O CCIS
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O PICTUREPHONES [SOONER THAN YOU THINK MY PHRIENDS]
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COMMON CONTROL SWITCHING ARRANGEMENTS ( CCSA ) PERMIT ANY UNRESTRICTED TELE-
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PHONE STATION TO CALL ANY OTHET INTERNAL OR EXTERNAL SYSTEM STATION BY USING
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THE STANDARD SEVEN DIGIT NUMBER.ALTERNATE ROUTING IS A FEATURE OF CCSA SERVICE
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THE INTERFACILITY,ALTERNATE ROUTED CALLING PATHS ARE ACCOMPLISHED AT THE TELE-
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PHONE COMPANY CENTRAL OFFICE LEVEL,NOT AT THE PBX LEVEL.
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A SYSTEM OF INTEREST TO LARGE SCALE TELEPHONE USERS IS COMMON CHANNEL INTER-
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OFFICE SIGNALLING (CCIS).TYPICALLY,THIS TECHNIQUE EMPLOYS COMMON CHANNELS TO
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CARRY ALL INTERFACILITY SIGNALLING INSTRUCTIONS: DIAL PULSES,ON HOOK (IDLE),
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OFF HOOK (BUSY),AND SO ON,BETWEEN TWO SWITCHING CENTERS. [ GETTING WARM ].
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CCIS REPLACES OLDER METHODS OF INTEROFFICE SIGNALLING SUCH AS 'IN BAND' AND
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'OUT OF BAND' TECHNIQUES. BY THE WAY,REAL PHREAKS ARE SELLING THEIR BOXES TO
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IDIOTS WHO STILL THINK THE'RE WORTH ALOT...THE FORMER (IN BAND) TRANSMITS
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SIGNALLING DATA WITHIN THE NORMAL CONVERSATION BANDWIDTH.IT'S SHORTCOMING IS
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THAT FALSE INFORMATION MAY BE TRANSMITTED DUE TO UNIQUE TONE OR NOISE
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COMBINATIONS SET UP IN THE TALKING PATH. [THIS IS THE OFFICIAL REASONING].
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OUT OF BAND SIGNALLING TECHNIQUES PLACED THE INTEROFFICE DATA IN SPECIAL
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CHANNELS,GENERALLY ADJACENT TO AND IMMEDIATELY ABOVE THE VOICE PATH.TO PRE-
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SERVE INTERCHANNEL INTEGRITY,OUT OF BAND SIGNALLING REQUIRES VERY EFFECIENT
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FILTERING OR GREATER 'BAND GUARD' SEPERATION BETWEEN CHANNELS.
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Brought to you in the Cookbook courtesy of the Jolly Roger!!!!!!!!!!!!
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