Ike Posted April 12, 2004 Share Posted April 12, 2004 Most telephone systems use a single pair although officially telephone wireing in domestic premesis should be three wire, the third wire being coupled to one of the main pair in the master socket. Link to comment Share on other sites More sharing options...
MarcT Posted April 13, 2004 Share Posted April 13, 2004 10/100Base-T does indeed only use two pairs (ie 4 wires). One pair is for transmit, the other for receive. This means that in most offices half the conductors in the CAT5 structured wiring are never even used! As you've seen, you can get adaptors to allow you to send two ethernet links down a single CAT5 (4 pairs) run. In my previous job, we used to make these ourselves - basically an RJ45 "Y" cable. One adapter is required at each end - so you still need to have enough ports on your hubs/switches. They're only useful if you're short on ethernet points. Most PBX (office) phone extensions use a single pair. Residential (analogue) phone circuits also only have a single pair coming into the premesis. However, as Ike mentions, three wires are used inside the premesis - the third being used to "ring" the phones. The "ring" signal is generated in the master socket using a capacitor/diode network. HTH,Marc Link to comment Share on other sites More sharing options...
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