What device provides power to a network device when the switch does not support PoE?

A power injector is a device specifically designed to provide power to a network device, such as an IP camera or VoIP phone, when the switch does not support Power over Ethernet (PoE). A power injector works by being placed in-line with the Ethernet cable that connects the device to the switch. It adds power to the Ethernet cable, allowing the network device to operate without needing a separate power source. This functionality is particularly useful for devices that require power but are located away from traditional power outlets.

In contrast, other devices mentioned do not serve this specific purpose. For instance, a router is primarily used to direct network traffic between different networks and does not provide PoE to connected devices. Similarly, a standard switch without PoE capabilities does not supply power and simply facilitates data transmission. A modem is used to connect a network to the internet and also does not provide power to network devices. Therefore, the power injector is the correct choice for supplying power in cases where PoE is unavailable.