The LAN, to date, has been utilized for Data Flow only. Central equipment such as, Hubs, Routers and Switches are plugged into the mains, as is the User Terminal. An independent infrastructure is the telephone system, in which the end terminal does not need to be connected to the mains.
Recent trends in telecommunications are attempting to marry traditional telephony with today's networks. IP Telephony converges voice and data, opening a new world of opportunities and features. This serves today's telephony well, until faced with a power failure or lack of a mains socket, presenting reliability issues. PowerDsine addresses this issue by injecting power over the spare pairs of the TIA/EIA-588 Category 5 and above cable. This in itself solves the IP telephone power problem and opens doors to new applications for the LAN.
PowerDsine Power over Ethernet technology converges power, voice and data by delivering an electrical supply and data communications over a single standard LAN cable. This eliminates the need for connecting each Ethernet terminal to both an electrical socket and a data outlet, thereby reducing a corporation's installation and maintenance costs. It also enhances system reliability by maintaining telephony service during power interruptions. In addition, the technology's ability to use a single uninterrupted power supply (UPS) for backup operations within the network enables enterprises to realize their full LAN potential and further reduce installation costs.
What is Power over Ethernet?
A Power over Ethernet system comprises of an Ethernet switch and a Power-Hub or a Power over Ethernet enabled Ethernet switch, which serves as the power source, and a number of Power enabled DTE, which are the loads. The system is a Star topology, where each load is connected with a dedicated connection to the centralized Power-Hub.
The Power-Hub is connected in series to an Ethernet switch/Hub (cascaded) where the Power-Hub inputs are connected to the switch outputs, and the Power-Hub outputs are connected to the patch panel. Power is carried over the spare twisted pairs (pins 7 & 8) and (pins 4 & 5) in an ordinary Category 5 and above cable with negligible degradation of data communication.
What does PowerDsine provide?
A Power over Ethernet Hub, Power-Hub, resembles a patch panel and has 6, 12 or 24 channels, injects the power to the LAN cables. The Power-Hub integrates internal power modules; each module contains a RJ-45 input Data connector and a RJ-45 output connector for the combined Data and Power. A passive module's input to output 10/100BaseT circuitry guaranties bi-directional data flow is maintained, regardless of the module's power status.
The PowerDsine SPEAR is an internal sophisticated power control and monitoring circuit. It is implemented on each of the power channels and activates the power only when a Power over Ethernet ready Ethernet terminal is present. This prevents the injection of power, and damage of devices such as ordinary NIC’s, which do not expect power on their Ethernet connection. The SPEAR also provides protection against channel overload and short circuit, reversed polarity caused by a faulty connection or a crossed cable and the connection of two feeding channels to each other.
Each PowerDsine Power-Hub provides remote power feeding for the 6, 12 or 24 terminals from a centralized universal AC input or an external DC power supply. The external 24/48Vdc input may be used to provide optional redundant power feeding. The -24V Power-Hub is designed to ensure at least 8W per output (measured at the channel output port) in order to deliver maximum of 5.6W at the device terminals (after reducing maximum of 100m cabling power drop). The -48V Power-Hub is designed to provide up to 13W at the device terminals. A single port Hub is also available either with -24Vdc or -48Vdc outputs.
How is Legacy Equipment Protected?
For a terminal to receive power on the Ethernet line it must be designed as such. Special detection routines are performed on each port before power is injected, in order to confirm that the terminal is ready. If equipment is not "Power Enabled" the Power-Hub will not supply power to that port. Equipment that is to be powered over the Ethernet is designed to be compatible with a particular Power-Hub and recognizable by it.
PowerDsine Power over Ethernet Application Notes can be downloaded from the PowerDsine Web site. The documents detail how the terminal recognition is performed, and how to build "Power Enabled" equipment.
PowerDsine was a founding member of the standards committee. More details can be found at the site: http://grouper.ieee.org/groups/802/3/af/index.html. If a device is incompatible with a Power-mid-span, an external splitter can be installed. The splitter separates the DC voltage and the Ethernet data signal into two separate wires, terminating at a power port and a RJ-45 jack.
How is the Terminal Interrogation Performed?
A PowerDsine Power-Hub interrogates the terminal by putting a constant voltage, current limited source on the wire pairs that are to be powered. A particular capacitive detection circuit is usually designed into equipment that is "Power Enabled". This circuitry returns the voltage in a certain manner that is analyzed by the Power-Hub microprocessor. Only if there is a recognized characteristic, will the Power-Hub inject Power down the line to the Terminal. Most Terminal units can be powered with a PowerDsine Power-Hub, even if they have not been specifically designed Power Enabled. As a minimum an external splitter can be utilized. The user should be in contact with
PowerDsine in order to certify the Terminal Power Enabled.
The interrogation process takes very short period of time, depending on the identification characteristics of the Terminal connected. It is repeated at regular intervals on each un-powered port. If a terminal is removed the channel will power down.
PowerDsine advocates the use of the spare wires in an ordinary Cat 5 cable, pairs 4,5 and 7,8. So only these lines are interrogated.
What could be expected if a voltage will be on the 1,2 & 3,6 pairs?
The benefit of the Power over Ethernet is the detection routine, this has high priority in the IEEE standards. Before power is injected to a terminal, the terminal will be 'interrogated' to see if it is "Power Enabled". This Interrogation will be performed on the same lines as the power is due to be supplied.
Therefore if no 'identification' is on pins 1,2,3,6 then no power will be supplied. A terminal will have to be designed correctly in order to receive power on those pins.
What is the AC/DC isolation in the power Hub?
The power supply of the Power-Hub is rated with 3KV insulation between its input and output.
Why should Isolation be used in the IP telephones?
The Power-Hub channels are not isolated from each other. [This is not required and would become very expensive]. This means that two terminals that are connected to ground, could be at different potentials and cause damage to the Power-Hub via Ground Loops. If a terminal does not have any external connections, which could be connected to ground, then it does not need to be isolated. i.e. the casing (if plastic) is acceptable isolation.
Regarding safety - which severance is met?
The Power-Hub is designed to Double Isolation Class 2. The unit is designed to meet UL, CSA and TUV.
Is the output voltage supply floating or earthed to ground?
The output voltage supply is floating.
Are the Power-Hubs ready for 1KV surge (2msec to 5msec)?
Yes, the Power-Hubs have been tested with transients on the input and output connections.
