Hi
From the 2960 switch FAQ
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Q. What are dual-purpose uplinks?
A. A dual-purpose uplink is a combination of one 10/100/1000-TX copper port and one SFP-based Gigabit Ethernet port. One of these two ports can be used at a time. This added uplink flexibility allows cost-effective use of high-density, fiber-uplink-based stacks. Dual-purpose uplinks also offer a full-duplex, gigabit-speed trunk for a Cisco Catalyst 2960 Series switch stack, an improvement over the half-duplex Cisco GigaStack? configuration.
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HTH
Jon