Content

| 7.6 |  | Network Design Issues for Voice |
| 7.6.3 |  | Power to IP Phones |

Cisco IP Phones support a variety of power options:

Inline Power
The advantage of inline power is that it does not require a local power outlet. Power is provided by the Ethernet switch and is passed to the IP phone through the four pair UTP cabling. This also permits centralization of power management facilities.

External Patch Panel Power
If the switch does not have a power-enabled line card, or one is not available for the switch being used, then a Cisco power patch panel can be used. The power patch panel can be inserted in the wiring closet between the Ethernet switch and the Cisco IP Phone.

The patch panel has a 250W power supply and draws its power from a 110 VAC source. It can accommodate 48 ports and is capable of supplying power to each of the 48 ports at 6.3W. An uninterruptible power supply (UPS) is recommended for backup in the event of a power failure.

The actual conductors used are pins 4 and 5 (pair 1) and pins 7 and 8 (pair 4) for power and ground return. This means that all four pairs in the Category 5 cable need to be terminated at the user's desk and in the wiring closet.

Wall Power
A third option is to power the Cisco IP Phone from a local transformer module plugged into a nearby outlet. The obvious drawback to individually powering the IP phones is the absence of centralized power protection and backup.

A combination of these power options can provide redundant power to the Cisco IP Phone.