I need both voice and data cable installed; is there any advantage to installing Cat 5e or Cat 6 for my phone system?

Having Cat 5e or 6 installed for both your data and phones offers you the flexibility to use your phone jacks as network jacks in the future (assuming you have the cables terminated onto a patch panel). If you use less than Cat 5 for your phones then your future use of those cables will be pretty much limited to that purpose. Note that while the price differential between Cat 5e and Cat 6 is getting slimmer the one disadvantage is still that a Cat 6 installation will still be more expensive.

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