Bell wire: Difference between revisions

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Telephones designed for the UK will use 3 wires - 'A', 'B', and 'bell'. Their bells will be connected between the bell wire and the 'A' wire. If used in an installation without a bell capacitor or without a bell wire, such telephones won't ring their bells. A good example is a plug-in electronic ringer I have - the BT phone plug has only 2 pins - for the bell wire and the 'A' 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.

The US telephone system is different, and each telephone provides its own bell capacitor - but in the US pulse dialling is rare (although exchanges still support it). They tackled bell tinkle mechanically. Telephones designed for the US market will ring without a bell capacitor or without a bell wire.

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.

The bell wire complicates DSL filtering - it's difficult having a twisted pair with only one wire. The best solution is a filtered master socket (e.g. NTE5c with VDSL SSFP), with the bell wire connected to all other sockets, and no microfilters. 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.

= BT plug/socket numbering =