by ericmark »
Sun Sep 24, 2017 5:06 pm
There are two wires used as it enters your house, then there is a master socket which turns it into three wires, the third wire works the bell, the polarity is swapped to make bell ring so if wrong way around then bell does not work, the master socket also has a spark gap to stop electrical storms damaging your phone. Sorry can't remember which way around the two wires go.
The phone socket only uses 3 of the 6 connections there are three types of plugs in general use, the old 1/4 inch jack plug, and the new RJ11 and similar and smaller RJ9 / RJ10 / RJ22 the latter normally found as part of the phone, the RJ11 is normally what is found on the phone socket, You can get filters for broad band where a RJ11 plug has a RJ11 socket for telephone and RJ10 for broad band.
Not a clue why but with RJ10 centre two contacts are used, and with RJ11 the 2 and 5 contacts are used and 3 for the bell. I found with a fax machine it swapped 2 and 5 which stopped the bell ringing.
However with cordless phones and computer modems the terminal 3 is not used and it does not matter if 2 and 5 swapped. It only matters with old hard wired phones.
The cable has twisted pairs, this twist helps stop interference so you need to use a pair and not one wire from one pair and another wire from other pair, also needs to be for telephone I used alarm wire as 4 pairs and wanted two sockets, found it picked up white noise.
The incoming socket should be open reach and from that socket it is all yours, but mothers house still has old brown box and an earth stake for the party line. Dad put phone lines everywhere and we really don't know where they run, but today only really need one socket with the cordless phone and router and may be one old one with bell for use in power cuts.