Bell wire: Difference between revisions
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Effects of eliminating the tinkling |
Be clearer on microfilters. Add table for pin allocation |
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The US telephone system is different, and each telephone provides its own bell capacitor - but the US doesn't use pulse dialling any more. Telephones designed for that market will ring without a bell capacitor or without a bell wire. |
The US telephone system is different, and each telephone provides its own bell capacitor - but the US doesn't use pulse dialling any more. Telephones designed for that market will ring without a bell capacitor or without a bell wire. |
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The bell wire complicates DSL filtering. The best solution is a filtered master socket (e.g. NTE5c with VDSL SSFP). If using microfilters on each telephone, some microfilters include a bell capacitor, but some others don't - I've not seen any which properly support the bell wire. |
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= BT plug/socket numbering = |
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This is a complete list of pin usage. Pin 1 is closest to the latch. |
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{| class="wikitable" |
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! Function !! Pin number || Notes |
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| 1 || || |
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| 2 || 'B' wire || Used to be guaranteed more negative voltage than 'A' wire |
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| 3 || Bell wire || To distribute ringing current, and eliminate tinkling |
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| 4 || Local earth || ''Needed for 'C' wire signalling, which is obsolete'' |
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| 5 || 'A' wire || |
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| 6 || 'C' wire || '' 'C' wire signalling is obsolete'' |
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