Avaya 555-245-600 Midspan Power Units, 1152A1 Power Distribution Unit, Power priority mechanism

Midspan Power Units

Power priority mechanism

The priority mechanism is implemented in order to handle cases where the power requested by the PDs exceeds the switch PoE capacity. This priority mechanism determines the order in which ports will be powered on after boot, and powered off if the power resources of the module are exhausted. Three user-configurable port power priority levels are available: low, high & critical. Within each priority level the lower the port number, the higher the priority (by default all the ports have low priority).

Disconnected power will be automatically reconnected to the PDs based on their priority, whenever there is an available power budget. Immediately after the PoE has booted up, it starts to supply power to the ports where a load is detected. Ports are powered up one after another, based on the port priority, until the limit is reached. Power calculation is based on the actual power consumption of the PD. After this, no more ports are powered up until the total power consumption drops lower than the limit. The limit is 18 Watts below the maximum PoE capacity. The remaining 18W are reserve power for a change in the power draw of PDs.

Midspan Power Units

1152A1 Power Distribution Unit

The official name for this device is the 1152A1 Power Distribution Unit, but the Midspan Power Unit can also be called a powered data unit (PDU) or a power over Ethernet (POE) device. The Midspan Power Unit is 1U in height (1.75 inches or 4.44 cm) and has 24 RJ45 data input jacks on the bottom row, and 24 data and power output RJ45 jacks. Data flow is unaffected if power is disrupted and if the endpoint does not require power. An example is a laptop computer that is connected to the 1152A1. The computer does not receive power from the 1152A1. If the

120-volt power is disrupted to the 1152A1, the computer data stream would not be affected. The 1152A1 unit provides a maximum of 200 watts or a peak of 16.8 watts per port. This unit powers any device that conforms to the 25-K Ohm resistive signature defined in the IEEE 802.3-2003 af standard. This unit also powers devices that use the nonstandard capacitive signature, such as Cisco IP telephones. The 1152A1 provides positive voltage on pins 4/5 and negative voltage on pins 7/8, which is one of the three methods as described by the IEEE 802.3af standard.

Designed usage

The Midspan Power Unit is designed to mount in a 19-inch data rack, or can be stacked up to four units high using the optional rubber feet. Its niche is to provide power to only those IP endpoints that need power. The alternative is to have a switch that incorporates power. However, any nonpowered device that uses that switch is not using the power capabilities of the switch, and does not justify the higher price per port of that switch. The Midspan Power Unit solves this problem by providing power without altering the network topology.

Issue 6 January 2008 169