Re: Audio Video and power over cat 5

[test_at_1-script_dot_com@xxxxxxx (DA)]

Chris W wrote:


> Does anyone know of an inexpensive device that will allow me to run both

> video and power to my cameras using cat 5 cable?  It would also be nice

> to have audio on one of the cameras as well.

> Are these things really all that complicated?  Can't I just wire up the

> connectors to a cat 5 cable myself?  What would be really nice is a box

> with 4 RJ45 jacks on one side and 4 audio and video on the other side
> that would also send power down all 4 lines from one power supply.
> That
> would really make for a clean installation.

Well, can't really do that easily with neither of the two components,
power and video: CAT5(E) cable is designed for balanced mode transmission
(symmetrical on both conductors) whereas the composite video output of a
camera is a common mode transmission (one of the conductors is grounded).
So, you need a balun (balanced-to-unbalanced) device for the transition
between the two media. Really short distances would be fine just straight
in, but if you'd be talking 100+ feet, you are going to need a balun. OTOH
some cameras have balanced output with which you don't need a balun. These
tend to be higher-end cameras.

On the power side you need some means of compensation for the voltage drop
in the cable. Basically, just over-powering on the power supply end so
that it's at acceptable lever when it shows up at the camera end.

NVT (www.nvt.com) makes nice devices that handle video/power/PTZ control
over UTP. Prepare to pay dearly for the power portion of the solution
though due to that compensation circuitry.

Good luck!

DA




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