The opportunity to provide power to network security devices such as cameras over the same cable that carries data has been possible for some time, but the acceleration in the number of IP network based security systems has seen an increasing number of manufacturers building the option of PoE into their equipment.
PoE technology allows DC power and data transmitted at high frequency to utilise the same Cat 5e ‘Ethernet’ cable without interference.
The benefits, not the least of which is the fact that separate power cables and power supplies do not have to be installed for each camera, can be quite significant in terms of the cost of a new IP network based surveillance system or retrofitting additional cameras to an existing system.
Further cost savings
On large projects, further cost savings can be achieved by employing non-certified electricians to install the cameras, and PoE provides an additional advantage for multi- national companies who require an integrated networked security system in that variations in power standards do not have to be taken into account.
PoE can improve camera reliability as it is designed to prevent power surges or under powering and the centrally supplied power can be backed-up by a UPS (Uninterrupted Power Supply). A word of warning though: the batteries which support UPSs will only be able to provide back-up power for a limited time.
The consequences of a loss of power to cameras and recording devices as a result if a network failure has to be taken into consideration for ‘mission critical’ security projects.
Check the specs
In order to avoid the possibility of power losses, when designing a system which will be relying on PoE, it is also important to check the power specifications of the powered device as some budget level network switches are not able to supply full power (Class 0 or 3) for all outputs.
PoE has added some new words and phrases to the security installer’s glossary of terms. These include:
PSE (Power Sourcing Equipment) are devices which are the source of power in a PoE designed system.
PD (Powered Device) is a device which obtains its power from PSE. It could be a surveillance camera, but increasingly access control readers and controllers, as well as intruder alarm systems, are being manufactured with PoE capability.
Endspan – When the PSE is a switch. it is called an ‘endspan’.
Midspan – When the PSE sits between a switch which does not support PoE and a PD, it is called a ‘midspan’.
Help is at hand in the form of the IEEE 802.3af specification to guide you through how to best capitalise on PoE and the more recently introduced PoE+, but, as always, take advantage of the training course provided by manufacturers.
