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ThoughtPhreaker

Hardware bridging

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Not sure whether or not this should go in Hardware Hacking or not, but here goes. Everybody has tried bridging two POTS lines together by just shorting the two pairs to each other, right? Why is it this method always makes the volume drop so much for the distant party? Is there a circuit you can use to remedy this?

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Not sure whether or not this should go in Hardware Hacking or not, but here goes. Everybody has tried bridging two POTS lines together by just shorting the two pairs to each other, right? Why is it this method always makes the volume drop so much for the distant party? Is there a circuit you can use to remedy this?

I think when you cross-connect two phone lines you are creating a massive impedance mismatch, which loads up the line, causing attenuation....

http://massis.lcs.mit.edu/archives/technical/how.phones.work

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You could get around that fairly easily by making a 4P4C crossover cable between two phones. The speaker output for one goes to the mic on the other, and vice versa.

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