If a PoE (Power over Ethernet) switch is unable to supply sufficient power to a network device, a midspan, also known as a PoE injector, should be used. A midspan is an external device that adds power to the Ethernet cable, thus providing the necessary power to the network device. This is particularly useful when existing network infrastructure cannot be upgraded to meet power requirements. According to Axis documentation, midspans are recommended to ensure adequate power delivery for network devices that require PoE.