CONTENTS
| INSIDE A TYPICAL MODERN BT SYSTEM X EXCHANGE |
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| Main Distribution Frame (MDF) | ||
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| The Distribution side of the MDF, where all the subscriber's lines arrive at | ||
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| Distribution side of the MDF | Fuses and links | |
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| The Exchange side of the MDF, where lines are forwarded on within the exchange | ||
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| System X Equipment | ||
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| Line Cards, four subscriber's lines per card | ||
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| Multiplex Cards | Processor Cards | Main processor, Memory & Hard Drives |
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| Ringing Supplies | System X Equipment Racks | |
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| Wideband, ISDN, DACS, ADSL, LDU & Private Circuits | ||
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| Wideband, ISDN, Kilostream & Megastream Equipment | ||
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| Digital Access Carrier System (DACS) | Private Circuits | |
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| ADSL equipment | Old Ringing Machine | |
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| Loop Diagnosis Units, which provide the 17070 line test facility | ||
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| Large Diesel Engine, which drives the Standby Generator | Cable Pressurisation Unit | |
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