49 lines
2.5 KiB
Plaintext
49 lines
2.5 KiB
Plaintext
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BLACK BOX MODS FROM JACK PLUG
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THE BLACK BOX CHARGE INHIBIT CIRCUIT CURRENTLY CIRCULATING
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AGAIN (6.1K RESISTOR, LED, CAPACITOR, DIODE, ETC) SEEMS NOT
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TO WORK ON SEVERAL SYSTEMS. A USEFUL MOD IS TO REPLACE THE
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EXISTING RESISTOR WITH A VARIABLE TYPE. CHOOSE EITHER A 0 TO
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10K OR A 0 TO 1K VALUE TYPE AS MANY INSTRUMENTS CAN BE
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"BALANCED" WITH QUITE LOW ADDITIONAL RESISTANCES. TRIMMERS OR
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PRESETS ARE THE CHEAPEST, BUT FOR EASY AND ACCURATE
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READJUSTMENT GO FOR THE MULTI-TURN CERMIT TYPE OR SIMILAR.
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TO SET-UP, INSTALL THE BLACK BOX AND SET THE RESISTOR TO ITS
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LOWEST VALUE POSITION (FULLY ANTI-CLOCKWISE). WITH THE BOX
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OFF, LIFT THE HANDSET AND CHECK FOR A DIALLING TONE. NOW
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SWITCH THE BOX "ON" AND CHECK THAT THE TONE REMAINS. THE NEXT
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STEP IS TO GRADUALLY INCREASE THE RESISTANCE, CHECK FOR THE
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DIAL TONE, INCREASE THE RESISTANCE, CHECK FOR THE TONE.... AND
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SO ON UNTIL A POINT IS REACHED WHERE THE DIAL TONE EITHER
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FLUTTERS OR DISAPPEARS COMPLETELY. AT THIS POINT DECREASE THE
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RESISTANCE S L I G H T L Y.
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WITH A VOLMETER CONNECTED IN PARALLEL ACROSS THE LINE YOU
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SHOULD NOTICE THE USUAL VOLTAGE DROP WHEN THE HANDSET IS
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LIFTED AND THE BLACK BOX OFF. wITH THE BLACK BOX ON, HOWEVER,
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THE OFF-HOOK VOLTAGE DROP SHOULD BE CONSIDERABLY LESS.
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IN USE, THE BOX SHOULD BE SWITCHED ON WHEN SOMEONE RINGS YOU
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OR WHEN YOU HEAR THE RINGING TONE OF THE PERSON YOU ARE
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CALLING. IF THERE IS ANY JUSTICE, WHEN THE BOX IS SWITCHED ON
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THE EXCHANGE METER WILL "SEE" THE VOLTAGE SWING ASSOCIATED
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WITH YOU REPLACING THE HANDSET AND STOP COUNTING. ENOUGH
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CURRENT REMAINS, HOWEVER, TO FIRE-UP THE MIC AND FACILITATE
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CONTINUANCE OF THE CONVERSATION. SOME ODD THINGS HAVE HAPPENED
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WHILST WATCHING OTHERS USE THIS DEVICE (!). AT ONE POINT, THE
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BOX SWITCH WAS CLICKED OFF AND ON QUICKLY DURING A
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CONVERSATION AND A DIGITISED VOICE ANNOUNCED THAT "RECALL IS
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NOT AVAILABLE, YOU WILL BE RECONNECTED TO THE CALLER," AND THE
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CREDIT DISPLAY IN THE PHONE BOX THAT HAD INITIATED THE CALL
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PROMPTLY STOPPED CLOCKING DOWN.
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I HOPE THIS IS OF USE TO SOMEONE. REGARDS: JACK PLUG.
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(BY THE WAY, I HAVE FOR SALE OR SWAP A "MOULD" SELCALL UNIT.
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FULLY OPERATIONAL WITH INTACT EPROM/CALLSIGN. WANT VERY CHEAP
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TNC OR RTTY INTERFACE. DESPERATELY NEED CIRCUITS/INFO ON
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"TEMPEST.")
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