Thursday, June 4, 2009

Digitally Controlled AGC

AGC (automatic gain control) is nothing new and is used in a variety of equipment from CCTV cameras to fibre optic transmission equipment. When it came time to implement AGC in our Fibre Lite range of products we decided to do something really special with the AGC.

We analysed the sort comings of traditional Gain Control on analogue fibre optic equipment and found that the biggest problem was video drift. Simply put this is when the image starts losing its contrast, colour and eventually video sync (the image rolls on the screen). Video drift is caused by a number of factors like; cable aging, electronic component aging, large temperature fluctuations, additional losses on the cable due to the cable being damaged and requiring some splicing work, etc.

The Gain Control is there to compensate for all these variables but it’s normally a manual adjustment. This means that the system requires regular servicing by a qualified technician to maintain a crisp high resolution image.

We thought that in today’s world of high labour costs and the low cost digital microprocessors; why not have a microprocessor continually sampling, analysing and adjusting the gain control? This is how we come up with the idea of Digitally Controlled AGC. In our Fibre Lite range each fibre optic video receiver has its own dedicated microprocessor continually sampling, analysing and adjusting the gain control. Below is a simple diagram of how it’s done.



This is the magic behind Fibre Lite and what makes the product range adjustment free without digitally encoding the video as is the case with our Fibre Pro range.

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