Is the following true or false? When Inline power is being used to supply power to an IP Phone, the Catalyst switch sends a special Fast Link Pulse (FLP) signal down the cable to discover whether or not the attached device is an IP Phone.
A.
True
B.
False
Explanation:
Cisco has been shipping its PoE solution since 2000 and currently has more than 16 million IP PoE ports installed. The currently shipping Cisco solution uses a differential discovery scheme based on a special tone. The PSE (Power Sourcing Equipment) sends a unique fast link pulse (FLP) over the transmit (Tx) pair. If the connected device is PoE-capable, it returns this FLP back to the switch. At this point, the switch recognizes that the attached device is PoE-capable and powers the device with the default power allocation. Cisco IP phones and wireless access points use the Cisco Discovery Protocol to subsequently refine the power requirement for the particular device. The current default allocation is 6.3W. The Cisco prestandard implementation uses the link signal of the port physical layer (PHY) to shut the port down. When the link is lost, power is removed from the port. Figure 1 shows this process of powering a Cisco powered device. Figure 1.Cisco Prestandard Powered-Device Power Delivery
