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Old 15th Jul 2018, 2:19 pm   #22
paulsherwin
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Location: Oxford, UK
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Default Re: Info. on 'phone requested

Quote:
Originally Posted by Biggles View Post
If it is a feature phone, it may have four wires. Typically on our mini-switches such as Panansonics the feature phone has extra functionality and works on four wires.
This really only applies to commercial systems though. All the domestic speakerphones I've ever come across are 2 wire with even the ring connection being unused. The commercial systems use 4 wires to support things like putting callers on hold or transferring the call to a different extension.

Of course, if you find a phone in a skip then it may well have come out of an office and require a 4 wire connection.
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