329 lines
16 KiB
Plaintext
329 lines
16 KiB
Plaintext
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*******BIOC AGENT 003 COURSE IN********
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* *
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* ========================== *
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* =BASIC TELECOMMUNICATIONS= *
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* ========================== *
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* PART V *
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***************************************
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PREFACE:
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PREVIOUS INSTALLMENTS OF THIS SERIES WERE FOCUSED ON TELEPHONY FROM A NETWORK
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POINT-OF-VIEW. PART V WILL DEAL WITH TELEPHONE ELECTRONICS FOCUSING
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PRIMARILY ON THE SUBSCRIBER'S TELEPHONE. HEREINAFTER SIMPLY REFERRED TO AS
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"FONE."
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WIRING:
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-------
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ASSUMING A STANDARD ONE-LINE FONE, THERE ARE USUALLY 4 WIRES THAT LEAD OUT OF
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THE FONE SET. THESE ARE STANDARDLY COLORED RED, CREEN, YELLOW, & BLACK. THE
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RED & GREEN SIRES ARE THE TWO THAT ARE ACTUALLY HOOKED UP TO YOUR CO. THE
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YELLOW WIRE IS SOMETIMES USED TO RING DIFFERENT FONES ON A PARTY LINE (IE,
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ONE #, SEVERAL FAMILIES--FOUND PRIMARILY IN RURAL AREAS WHERE THEY PAY LESS
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FOR THE SERVICE AND THEY DON'T USE THE FONE AS MUCH); OTHERWISE, THE YELLOW
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IS USUALLY JUST IGNORED. ON SOME TWO-LINE FONES, THE RED & GREEN WIRES ARE
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USED FOR THE FIRST FONE # AND THE YELLOW & BLACK ARE USED FOR THE SECOND LINE
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. IN THIS CASE THERE MUST BE AN INTERNAL OR EXTERNAL DEVICE THAT SWITCHES
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BETWEEN THE TWO LINES AND PROVIDES A HOLD FUNCTION. (SUCH AS RADIO SHACK'S
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OUTRAGEOUSLY PRICED 2 LINE & HOLD MODULE9.
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IN TELEPHONY, THE RED & GREEN WIRES ARE OFTEN REFERRED TO AS TIP (T) & RING
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(R). THE TIP IS USUALLY THE MORE POSITIVE OF THE TWO WIRES. THIS NAMING
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GOES BACK TO THE OLD OPERATOR CORD BOARDS WHERE ONE OF THE WIRES WAS THE TIP
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OF THE PLUG AND THE OTHER WAS THE RING (OF THE BARREL).
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A ROTARY FONE (AKA DIAL OR PULSE) WILL WORK FINE REGARDLESS WHETHER THE RED
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(OR GREEN) WIRE IS CONNECTED THE TIP(+) OR RING(-). A TOUCH-TONE (TM) FONE
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IS A DIFFERENT STORY, THOUGH. IT WILL NOT WORK EXCEPT IF THE TIP(+) IS THE
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GREEN WIRE. [ALTHOUGH, SOME OF THE MORE EXPENSIVE DTMF FONES DO HAVE A
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RECTIFIER BRIDGE WHICH COMPENSATES FOR POLARITY REVERSAL.] THIS I WHY UNDER
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CERTAIN (NON-DIGITAL) SWITCHILG EQUIPMENT YOU CAN REVERSE THE RED & GREEN
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WIRES ON A TOUCH-TONE FONE AND RECEIVE FREE DTMF SERVICE. EVEN THOUGH IT WON
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'T BREAK DIAL TONE, REVERSING THE WIRES ON A ROTARY LINE ON A DIGITAL SWITCH
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WILL CAUSE THE TONES TO BE GENERARTED.
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VOLTAGES, ETC.
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--------------
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WHEN YOUR TELEPHONE IS ON-HOOK (IE, HUNG UP) THERE IS APPROXIMATELY 48 VOLTS
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OF DC CURRENT (VDC) FLOWING THROUGH THE TIP & RING. WHEN THE HANDSET OF A
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FONE IS LIFTED A FEW SWITCHES CLOSE WHICH CAUSE A LOOP TO BE CONNECTED (KNOWN
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AS THE "LOCAL LOOP") BETWEEN YOUR FONE & THE CO. ONCE THIS HAPPENS DC
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CURRENT IS ABLE TO FLOW THROUGH THE FONE WITH LESS RESISTANCE. THIS CAUSES A
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RELAY TO ENERGIZE WHICH CAUSES OTHER CO EQUIPMENT TO REALIZE THAT YOU WANT
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SERVICE. EVENTUALLY, YOU SHOULD END UP WITH A DIAL TONE. THIS ALSO CAUSES
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THE 48 VDC TO DROP DOWN INTO THE VICINITY OF 13 VOLTS. THE RESISTANCE OF THE
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LOOP ALSO DROPS BELOW THE 2500 OHM LEVEL.
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AS OF NOW, YOU ARE PROBABLY SAYING TO YOURSELF THAT THIS IS ALL NICE AND
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TECHNICAL BUT WHAT THE HELL GOOD IS THE INFORMATION. WELL, ALSO CONSIDER
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THAT THIS VOLTAGE (& RESISTANCE) DROP IS HOW THE CO DETECTS THAT A FONE WAS
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TAKEN OFF HOOK (PICKED UP). IN THIS WAY, THEY KNOW WHEN TO START BILLING THE
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CALLING NUMBER. NOW WHAT DO YOU SUPPOSE WOULD HAPPEN IF A DEVICE SUCH AS A
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RESISTOR OR A ZENER DIODE WAS PLACED ON THE CALLED PARTIES LINE SO THAT THE
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VOLTAGE WOULD DROP JUST ENOUGH TO ALLOW TALKING BUT NOT ENOUGH TO START
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BILLING? FIRST OFF, THE CALLING PARTY WOULD NOT BE BILLED FOR THE CALL BUT
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CONVERSATION COULD BE PERSUED. SECONDLY, THE CO EQUIPMENT WOULD THINK THAT
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THE FONE JUST KEPT ON RINGING. THE TELCO CALLS THIS A "NO-NO" (TOLL FRAUD TO
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BE MORE SPECIFIC) WHILE PHONE PHREAKS AFFECTIONATELY CALL THIS MUTE A BLACK
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BOX.
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THE FOLLOWING ARE INSTRUCTIONS ON HOW TO BUILD A SIMPLE BLACK BOX. OF COURSE
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, ANYTHING THAT PREVENTS THE VOLTAE FROM DROPPING WOULD WORK.
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YOU ONE OR TWO PARTS: A SPST TOGGLE SWITCH AND A 10,000 OHM (10 K), 1/2 WATT
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RESISTOR. ANY ELECTRONICS STORE SHOULD STOCK THESE PARTS. NOW, CUT 2 PIECES
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OF WIRE (ABOUT 6 INCHES LONG) AND ATTACH ONE END OF EACH WIRE TO ONE OF THE
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TERMINALS ON THE SWITCH. NOW TURN YOUR K500 (STANDARD DESK FONE) UPSIDE DOWN
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AND TAKE OFF THE COVER. LOCATE THE 2 SCREWS ON THE NETWORK BOX LABELED >F<
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AND >RR<. WRAP THE RESISTOR BETWEEN THE 2 SCREWS MAKING SURE THAT IT DOESN'T
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TOUCH ANY OTHER TERMINALS!. NOW CONNECT ONE WIRE FROM THE SWITCH TO THE RR
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TERMINAL. FINALLY, ATTACH THE REMAINING WIRE TO THE GREEN WIRE (DISCONNECT
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IT FROM ITS TERMINAL). NOW BRING THE SWITCH OUT THE REAR OF THE FONE AND
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REPLACE THE COVER.
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PUT THE SWITCH IN A POSITION WHERE YOU RECEIVE A DIAL TONE. MARK THIS
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POSITION NORMAL. MARK THE OTHER SIDE FREE.
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WHEN YOUR PHRIENDS CALL (AT A PREARRANGED TIME), QUICKLY LIFT & DROP THE
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RECEIVER AS FAST A POSSIBLE. THIS WILL STOP THE RINING (DO IT AGAIN IF IT
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DOESN'T) WITH OUT STARTING THE BILLING. IT IS IMPORTANT THAT YOU DO IT
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QUICKLY (LESS THAN ONE SECOND THEN PUT THE SWITCH IN THE FREE POSITION AND
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PICK UP THE FONE. KEEP ALL CALL SHORT AND PREFERRABLY UNDER 15 MINUTES.
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NOTE: IF ANYONE PICKS UP AN EXTENSION IN THE CALLED PARTIES HOUSE AND THAT
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FONE IS NOT SET FOR FREE THEN BILLING WILL START.
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NOTE #2: AN OLD WAY OF SIGNADLING A PHRIEND THAT YOU ARE ABOUT TO CALL IS
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MAKING A COLLECT CALL TO A NON-EXISTANT PERSON IN THE HOUSE. SINCE YOUR
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FRIEND WILL NOT ACCEPT THE CHARGES, HE WILL KNOW THAT YOU ARE ABOUT TO CALL
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AND THUS PREPARE THE BLACK BOX (OR VISA VERSA).
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WARNING: THE TELCO CAN DETECT BLACK BOXES IF THEY SUSPECT ONE ON YOUR LINE.
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THIS IS DONE DUE TO THE PRESENCE OF AC VOICE SIGNAL AT THE WRONG DC LEVEL!
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PICTORAL DIAGRAM:
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(STANDARD ROTARY K500 FONE)
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---------------------------------------
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! !
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***BLUE WIRE**>>F< !
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! * * !
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**WHITE WIRE** * !
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! * !
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! REISTOR !
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! * !
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! * !
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! >RR<*******SWITCH**** !
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! * !
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****GREEN WIRE********************** !
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! !
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---------------------------------------
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NOTE: THE BLACK BOX WILL NOT WORK UNDER ESS OR OTHER SIMILAR DIGITAL
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SWITCHES SINCE ESS DOE NOT CONNECT THE VOICE CIRCUITS UNTIL THE FONE IS
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PICKED UP (& BILLING STARTS). INSTEAD, ESS USES AN "ARTIFICIAL" COMPUTER
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GENERATED RING.
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RINGING:
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--------
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TO INFORM A SUBSCRIBER OF AN INCOMING CALL, THE TELCO SENDS 90 VOLTS (RMS) OF
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AC CURRENT DOWN THE LINE (AT AROUND 15 TO 60 HZ) IN STANDARD FONES, THIS
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CAUES A METAL ARMATURE TO BE ATTRACTED ALTERNATELY BETWEEN TWO ELECTRO
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-MAGNETS THUS STRIKING 2 BELLS. OF COURSE, THE STANDARD BELL (PATENTED IN
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1878 BY TOM A. WATSON) CAN BE REPLACED BY A MORE MODERN ELECTRONIC BELL OR
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SIGNALING DEVICE.
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ALSO, YOU CAN HAVE LIGHTS AND OTHER SIMILAR DEVICES IN LIEU OF (OR IN
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CONJUNCTION WITH) THE BELL. A SIMPLE NEON LIGHT (WITH ITS CORRESPONDING
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RESISTOR) CAN SIMPLY BE CONNECTED BETWEEN THE RED & GREEN WIRES (USUALLY L1 &
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L2 ON THE NETWORK BOX) SO THAT IT LIGHTS UP ON INCOMING CALLS. A REGULAR 60
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WATT LIGHT BULB CAN ALSO BE HOOKED UP USING A SIMPLE (120 VAC) RELAY.
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WARNING: 90 & 120 VAC CAN GIVE QUITE A SHOCK. EXERCISE EXTREME CAUTION IF
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YOU WISH TO FURTHER PERSUE THESE TOPICS.
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ALSO INCLUDED IN THE RINGING CIRCUIT IS A CAPACITOR TO PREVENT THE DC CURRENT
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FROM INTERFERRING WITH THE BELL [A CAPACITOR WILL PASS AC CURRENT WHILE IT
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WILL PREVENT DC CURRENT FROM FLOWING (BY STORING IT)].
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ANOTHER REASON THAT THE TELCO HATES BLACK BOXES IS BECUASE RINGING USES ALOT
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OF COMMON-CONTROL EQUIPEMET, IN THE CO, WHICH USE ALOT OF ELECTRICITY. THUS
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THE RINGING GENERATORS ARE BEING TIED UP WHILE A FREE CALL IS BEING MADE.
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USUALLY CALLS THAT ARE ALLOWED TO RING FOR A LONG PERIOD OF TIME MAY BE
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CONSTRUED AS SUSPICIOUS. SOME OFFICES MAY BE SET UP TO DROP A TROUBLE CARD
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FOR LONG PERIODS OF RINGING THEN A "NO-NO" DETECTION DEVICE MAY BE PLACED ON
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THE LINE.
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INCIDENTALLY, THE TERM "RING TRIP" REFERS TO THE CO PROCESS INVOLVED TO STOP
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THE AC RINGING SIGNAL WHEN THE CALLING FONE GOES OFF HOOK.
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NOTE: IT IS SUGGESTED THAT YOU ACTUALLY DISSECT FONES TO HELP YOU BETTER
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UNDERSTAND THEM. IT WILL ALSO HELP YOU TO BETTER UNDERSTAND THE CONCEPTS
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HERE IF YOU ACTUALLY PROVE THEM TO YOURSELF. FOR EXAMPLE, ACTUALLY TAKE THE
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VOLTAGE READINGS ON YOUR FONE LINE [ANY SIMPLE MULTI-TESTER (A MUST) WILL DO.
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] PHREAKING IS AN INTERACTIVE PROCESS NOT A PASSIVE ONE!
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DIALING:
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--------
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ON A STANDARD FONE, THERE ARE TWO COMMON TYPES OF DIALING: PULSE & DTMF. OF
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COURSE, SOME PEOPLE INSIST UPON BEING DIFFERENT AND DON'T USE THE DT THUS
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LEAVING THEM WITH MF (MULTI FREQUNCY, AKA OPERATOR, BLUE BOX) TONES. THIS IS
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ANOTHER "NO-NO" AND THE TELCO SECURITY GENTELMEN HAVE A SPECIAL KNACK FOR
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DEALING WITH SUCH "PHREAKS" ON THE NETWORK.
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WHEN YOU DIAL ROTARY, YOU ARE ACTUALLY RAPIDLY BREAKING & RECONNECTING
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(MAKING) THE LOCAL LOOP ONCE FOR EVERY DIGIT DIALED. SINCE THE PHYSICAL
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CONNECTION MUQT BE BROKEN, YOU CANNOT DIAL IF ANOTHER EXTENSION (OF THAT #)
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IS OFF-HOOK. NEITHER OF THE FONES WILL BE ABLE TO DIAL PULSE UNLESS THE
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OTHER HANGS UP.
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ANOTHER TERM OFTEN REFERRED TO IN TELEPHONE ELECTRONICS IS THE BREAK RATIO.
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IN THE US, THERE ARE 10 PULES PER SECOND (MAX). WHEN THE CIRCUIT IS OPENED
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IT IS CALLED THE BREAK INTERVAL. WHEN IT IS CLOSED IT IS CALLED THE MAKE
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INTERVAL. IN THE US, THERE IS A 60 MILLISECOND (MS) BREAK PERIOD AND A 40 MS
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MAKE PERIOD. (60+40=100 MS = 1/10 MINUTE). THIS IS REFERRED TO AS A 60%
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BREAK INTERVAL. SOME OF THE MORE SOPHISTICATED ELECTRONIC FONES CAN SWITCH
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BETWEEN A 60% & A 67% BREAK INTERVAL. THIS IS DUE TO THE FACT THAT MANY
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FOREIGN NATIOS USE A 67% BREAK INTERVAL.
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HAVE YOU EVER BEEN IN AN OFFICE OR A SIMILAR FACILITY AND SAW A FONE WAITING
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TO BE USED FOR A FREE CALL BUT SOME ASSHOLE PUT A LOCK ON IT TO PREVENT
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OUTGOING CALLS?
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WELL, DON'T FRET PHELLOW PHREAKS, YOU CAN SIMULATE PULSE DIALING BY RAPIDLY
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DEPRESSING THE SWITCHOOK. (IF YOU DEPRESS IT FOR LONGER THAN A SECOND IT
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WILL BE CONSTRUED AS A DISCONNECT.) BY RAPIDLY SWITCHOOKING YOU ARE CAUSING
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THE LOCAL LOOP TO BE BROKEN & MADE SIMILAR TO ROTARY DIALING! THUS IF YOU
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CAN MANAGE TO SWITCHOOK RAPIDLY 10 TIMES YOU CAN REACH AN OPERATOR TO PLACE
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ANY CALL YOU WANT! THIS TAKES ALOT OF PRACTICE, THOUGH. YOU MIGHT WANT TO
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PRACTICE ON YOUR OWN FONE DIALIN A FRIEND'S # OR SOMETHING ELSE.
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INCIDENTALLY, THIS METHOD WILL ALSO WORK WITH DTMF FONES SINCE ALL DTMF LINES
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CAN ALSO HANDLE ROTARY.
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ANOTHER PROBLEM WITH PULSE DIALING IS THAT IT PRODUCES HIGH-VOLTAGE SPIKES
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THAT MAKE LOUD NOISES IN THE EARPIECE AND CAUSE THE BELL TO "TINKLE." IF YOU
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NEVER NOTICED THIS THEN YOUR FONE HAS A SPECIAL "ANTI-TINKLE" & EARPIECE
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SHORTING CIRCUIT (MOST DO). IF YOU HAVE EVER DISSECTED A ROTARY FONE (A MUST
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FOR ANY SERIOUS PHREAK) YO WOULD HAVE NOTICED THAT THERE ARE 2 SETS OF
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CONTACT THAT OPEN AND CLOSE DURING PULSING (ON THE BACK OF THE ROTARY DIAL
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UNDER THE PLASTIC COVER). ONE OF THESE ACTUALLY OPENS AND CLOES THE LOOP
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WHILE THE OTHER MUTES THE EARPIECE BY SHORTING IT OUT. THE SECOND CONTACTS
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ALSO ACTIVATES A SPECIAL ANTI-TINKLE CIRCUIT THAT PUTS A 340 OHM RESISTOR
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ACROSS THE RINGING CIRCUIT WHICH PREVENTS THE HIGH VOLTAGE SPIKES FROM
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INTERFERRING WITH THE BELL.
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DUAL TONE MULTI FREQUENCY (DTMF) IS A MODERN DAY IMPROVEMENT ON PULSE DIALING
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IN SEVERAL WAYS. FIRST OF ALL, IT IS MORE CONVENIENT FOR THE USER SINCE IT
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IS FASTER AND CAN BE USED FOR SIGNALING AFTER THE CALL IS COMPLETED (IE,
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SCC'S, COMPUTERS, ETC.). ALSO, IT IS MORE UPTO PAR WITH MODERN DAY SWITCHING
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EQUIPMENT (SUCH AS ESS) SINCE PULSE DIALING WAS DESIGNED TO ACTUALLY MOVE
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RELAYS BY THE NUMBER OF DIGITS DIALED (IN SXS OFFICES).
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EACH KEY ON A DTMF KEYPAD PRODUCES 2 FREQUENCIES SIMULTANEOUSLY (ONE FROM THE
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HIGH GROUP AND ANOTHGR FROM THE LOW GROUP).
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-------------------------
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LOW GROUP ! Q ! ABC ! DEF ! !
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697 HZ-! 1 ! 2 ! 3 ! A !
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! ! ! ! !
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!-----!-----!-----!-----!
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! GHI ! JKL ! MNO ! !
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770 HZ-! 4 ! 5 ! 6 ! B !
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! ! ! ! !
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!-----!-----!-----!-----!
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! PRS ! TUV ! WXY ! !
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852 HZ-! 7 ! 8 ! 9 ! C !
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! ! ! 1 !
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!-----!-----!-----!-----1
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! ! OPER! ! !
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941 HZ-! * ! 0 ! # ! D !
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! ! Z ! ! !
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!-----!-----!-----!-----!
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1209 1336 1477 1633
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(HIGH GROUP--IN HZ)
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A PORTABLE DTMF KEYPAD IS KNOWN AS A WHITE BOX.
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THE FOURTH COLUMN (1633 HZ) IS NOT NORMALLY FOUND O REGULAR FONES BUT IT DOES
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HAVE SEVERAL SPECIAL USES. FOR ONE, IT IS USED TO DESIGNATE THE PRIORITY OF
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CALLS ON AUTOVON, THE MILITARY FONE NETWORK. THESE KEY ARE CALLED: FLASH,
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IMMEDIATE, PRIORITY, & ROUTINE (WITH VARIATIONS) INSTEAD OF ABCD. SECONDLY,
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THESE KEYS ARE USED FOR TESTING PURPOSES BY THE TELCO. IN SOME AREA YOU CAN
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FIND LOOPS AS WELL AS OTHER NEAT TESTS (SEE PART II) ON THE 555-1212
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DIRECTORY ASSISTANCE EXCHANGE. FOR THIS, YOU WOULD CALL UP AN DA IN CERTAIN
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AREAS [THAT HAVE AN AUTOMATIC CALL DISTRIBUTOR (ACD)] AND HOLD DOWN THE "D"
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KEY WHICH SHOULD BLOW THE OPERATOR OFF. YOU WILL THEN HEAR A PULSING DIAL
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TONE WHICH INDICATES THAT YOU ARE IN THE ACD INTERNAL TESTING MODE. YOU CAN
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GET ON ONE SIDE OF A LOOP BY DIALING A 6. THE OTHER SIDE IS 7. SOME PHREAKS
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CLAIM THAT IF THE PERSON ON SIDE 6 HANGS UP, OCCASIONALLY THE EQUIPMENT WILL
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SCREW UP AD START DIRECTING DIRECTORY ASSISTANCE CALLS TO THE OTHER SIDE OF
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THE LOOP. ANOTHER ALLEGED TEST IS CALLED REMOB WHICH ALLOWS YOU TO TAP INTO
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LINES BY ENTERING A SPECIAL CODE FOLLOWED BY THE 7 DIGIT NUMBER YOU WANT TO
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MONITOR. THEN THERE IS THE POSSIBILITY OF MASS CONFERENCING.
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ACD'S ARE BECOME RARE THOUGH. YOU WILL PROBABLY HAVE TO MAKE SEVERAL NPA-555
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-1212 CALLS BEFORE YOU FIND ONE.
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YOU CAN MODIFY REGULAR FONES QUITE READILY SO THAT THEY HAVE A SWITCH TO
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CHANGE BETWEEN THE 3RD AND 4TH COLUMNS. THIS IS CALLED A SILVER BOX (AKA
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GREY BOX) AD PLANS CAN BE FOUND IN TAP AS WELL AS ON MANY BBS'S.
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TRANSMITTER/RECEIVER:
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---------------------
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WHEN YOU TALK INTO THE TRANSMITTER, THE SOUND WAVES FROM YOUR VOICE CAUSE A
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DIAPHRAGM TO VIBRATE AND PRESS AGAINST THE CARBON GRANULES (OR ANOTHER
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SIMILAR SUBSTANCE). THIS CAUSES THE CARBON GRANULES TO COMPRESS AND CONTRACT
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THUS CHANGING THE RESISTANCE OF THE DC CURRENT FLOWING THROUGH IT. THEREFORE
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, YOUR AC VOICE SIGNAL IS SUPERIMPOSED OVER THE DC CURRENT OF THE LOCAL LOOP.
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THE RECEIVER WORKS IN A SIMILAR FASHION WHERE THE SIMPLE TYPES UTILIZE A
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MAGNET, ARMATURE, & DIAPHRAGM.
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HYBRID/INDUCTION COIL:
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----------------------
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AS YOU MAY HAVE NOTICED, THERE ARE TWO WIRES FOR THE RECEIVER AND TWO FOR THE
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TRANSMITTER IN THE FONE, YET THE LOCAL LOOP CONSISTS OF 2 WIRES INSTEAD OF 4.
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THIS 4-WIRE TO 2-WIRE CONVERSION IS DONE INSIDE THE FONE BY A DEVICE KNOWN
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AS AN INDUCTION COIL WHICH USES COUPLING TRANSFORMERS.
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THE REASON 2 SIRES ARE USED ON THE LOCAL LOOPS ARE BECAUSE IT IS ALOT CHEAPER
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FOR THE TELCO. ALTHOUGH, ALL OF THE INTER-OFFICE TRUNKS UTILIZE 4 WIRES.
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THIS IS NECESSARY FOR FULL DUPLEX (IE, SIMULTANEOUS CONVERSATION ON BOTH
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SIDES) AND FOR AMPLIFICATION DEVICES. THERE ARE SIMILAR DEVICES IN THE CO'S,
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KNOWN AS A HYBRID, THAT COUPLE THE 4-WIRE TRUNKS TO THE 2-WIRE LOCAL LOOPS
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AND VISA-VERSA.
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MISCELLANEOUS:--------------
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IN THE TELEPHONE, THERE IS ALSO A BALANCING NETWORK CONSISTING OF A FEW
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CAPACITORS & RESISTORS WHICH PROVIDE SIDETONE. SIDETONE ALLOWS THE CALLER TO
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HEAR HIS OWN VOLUME IN THE RECEIVER. HE CAN THEN ADJUST HIS VOICE
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ACCORDINGLY. THIS PREVENTS PEOPLE FROM SHOUTING OR SPEAKING TOO SOFTLY
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WITHOUT NOTICING IT.
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HOLD:
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WHEN A TELEPHONE GOES OFF HOOK, THE RESISTANCE DROPS BELOW 2500 OHMS. AT
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THIS POINT, THE TELCO WILL SEND A DIAL TONE. TO PUT SOMEONE ON HOLD YOU MST
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PUT A 1000 OHM RESISTOR (1 WATT) ACROS THE TIP & RING BEFORE IT REACHES THE
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SWITCHOOK. IN THIS WAY, WHEN THE FONE IS HUNG UP (FOR HOLD) THE RESISTANCE
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REMAINS BELOW 2500 OHMS WHICH CAUSES THE CO TO BELIEVE THAT YOU ARE STILL OFF
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-HOOK.
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*****BIOC
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*=$=*AGENT
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*****003
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This phile was passed through Damage, Inc.
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