Final answer:
A technician should recommend a switch with Power over Ethernet (PoE) capabilities for a customer wanting to use VoIP phones without an electrical outlet, as it allows the network cables to deliver power to the devices.
Step-by-step explanation:
If a customer wants to use VoIP phones without the need to plug them into an electrical outlet, a technician should recommend a switch with Power over Ethernet (PoE) capabilities. This feature allows the network cables to carry electrical power to the device, in addition to data connectivity, thereby eliminating the need for a separate power source. This is particularly useful for devices like VoIP phones, wireless access points, and IP cameras.
Other options, such as Quality of Service (QoS), may be important for prioritizing traffic and maintaining call quality, but only PoE provides the power necessary to operate the phones without an outlet. Gigabit refers to the speed of the network and is not directly related to power, and Wake-on-LAN is a feature that allows a computer to be turned on or woken up by a network message, which is also not related to power provision.