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Fitting new cable to the bit before the master phone socket


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Old 16-02-2012, 13:13
John146
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Join Date: May 2008
Location: Lancashire
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The idea of the master socket is, customers CAN add their own stuff (providing uk telecom approved). Hence, the protector in master socket. Prior to that. the only plug & socket stuff was some key & lamp units with 4 wire BT jacks (NOT PO jacks!). And commercial PABXs of course ......
First of all Key & Lamp Units (now defunct) had a minimum of 21 wires between each terminal depending on the size of the Key & Lamp Units,, I suspect what you are referring to is the old POTS Plan 4 which was indeed a plug and socket system but had a separate bell fitted somewhere at the customers premises, and the sockets did have 4 wires, 2 line wires, one bell wire, and one bell shunt wire.
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Old 17-02-2012, 13:02
spiney2
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The basic idea of the rj plug is, various approved devices may be connected in parallel to line, as customer desires.Hence, some form of protection is required.

Under the older system domestic premises were directly hardwired to the junction box, and commercial premises had limited scope plugging arrangements,
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