Cooperman

Hi wOun, I must admit. I'd never heard of Magnavox till you mentioned them, and now I know why. Had a quick look up of some old information, and there was a small company called Magnavox listed for an address in Fort Wayne, Indiana, which is probably why we never managed to see their product this side of the pond. Anyhow, first guess is the lens is almost certainly (99% sure) 'C' mount. 'ES' probably refers to an auto iris lens (video iris); if it is, you should see two small externally accessible 'pots', one marked ALC and the other Level. If that is the case, it would be safer sticking to auto iris operation, rather than trying to manually overide it (some you can, some you can't!). I used to use a lot of Cosmicar (Pentax) lenses, but haven't had to deal with the catalogue numbers for many many years. Just from memory, the 'C' refers to 2/3" format, '6' is the zoom ratio, 'Z' can't remember!, '12' the shortest focal length, '18' is the iris (f1.8 ), 'M2' I think refers to motorised zoom and focus, and ES-2 was the later series built in auto iris amp. I'll have to get back to you on the wiring scheme for the zoom and focus (it's buried deep in the bowels of the building (and my mind!), although I can say with reasonable certainty that for the 'iris' red was always +ve voltage, black -ve, white 'video' from the lens connector on the camera; green (and also yellow) were used (on a few lenses) as manual overides on the iris control, but are generally redundant conductors to be cut back and insulated. If you have two cables, I'm guessing that one is for the iris, and the other is for zoom and focus. As to the lens voltage, therein lies a small problem; if I remember correctly, these lenses were available both as 12v DC (standard) and also 6v DC to special order. If you look at the motors it may give you a clue. If in doubt start with 6v DC and if the motor speed is painfully slow, you know it's probably 12v. I don't recognise the description for the connectors your trying to locate - does the socket have a screw thread around the outside? If you need to buy additional lenses, stick to 2/3" 'C' mount and you should be o.k. Just for future reference, if you buy a 'C' lens and the camera turns out to be 'CS', you only need to screw on a 5mm spacer ring (C:CS mount adaptor) to make it work. If I can find the wiring scheme in the next day or so, I'll get back to you.

In our neighbourhood, it's standard practice to earth 24v AC cameras, so there's exactly the same risk of earth loop, as if they were mains voltage. That's the main reason why I prefer 12v DC and hardly ever use 24v AC.

Manufacturers being less than truthful with specifications .... surely not What is the world coming to ....

Hi rory, If the cameras are 12v DC, and the case is insulated from any contact with metalwork, you shouldn't have any problem. Incidentally, check your PM's when you have a moment.

antdickens, If you want to trace the cause of the interference, you are going to have to 'break down' the system, and reconnect bit by bit until the problem re-appears. It may be a pain in the a**e, but their really is no short cut. The power supplies may well have caused the problem, but unless you isolate key components one at a time, you won't get anywhere fast. Incidentally, when you tested the video out on each camera, were the power supplies disconnected from all the other cameras, or were you still powering 3, and testing them one after another?

Rory, If you think we've got a lot of IR lamps, you should see the number of cameras!! The most recent industry estimates say there are around 4.2 million CCTV cameras being used in the U.K. The IR filter values for UK lamps have historically been based on 715nM & 830nM, with 850nM, 915nM, 950nM and 1000nM all being available at one time or another. Whilst it's right that most B/W cameras will work at 850nM, sensitivity is generally only around the 20 - 30% of that found when using visible light.

Shocking isn't it Pleased to hear you got it sorted ccolvard; it's often the little things .... Rory, Are you sure the dome covers are o.k? cable terminnations? I've had three hours sleep so I'm not far behind you

Bruno, Hard to believe, but the technology has actually existed for over thirty years. They used to be called Silicon Vidicon and Extended Red Newvicon tubes (also Ultricons which were manufactured by RCA). AVCONSULTING is spot on in his posting. Just a couple of things to add though; The average B/W CCD sensor has very poor Infra Red (IR) sensitivity above about 800 - 820nM, so this means you need shed loads more IR light at the higher (invisible) frequencies, than you would at the lower frequencies, simply to achieve the same picture. There are a few cameras that use very IR sensitive imagers, and these do cost quite a bit more than an average model, but the advantage is you get much clearer images even at distance with higher (covert) frequency IR. One final point; Tungsten bulb based illuminators use a glass filter to block most of the visible light from the lamp, but they actually pass a spread of frequencies, so for example, with an 830nM illuminator, the actual IR frequencies passed may be between 745nM > 900nM (with maximum peak energy output at around the 830nM mark). With LED based illuminators, the frequency band is much tighter, so you generally only have perhaps +/- 30nM against the manufacturers quoted figure. I suppose the simple answer to your question as to why all cameras don't use covert IR, is simply that they'd cost too much for most applications.

cctvfan, Possibly two seperate issues here. Firstly without knowing what the cameras are looking at, and what the available lighting is going to be, I would have suggested that Direct Drive or Auto Iris would be a safer bet. That said, my personal preference would be to use a manual iris lens with Electronic Iris (CCD Iris) function wherever practical / possible (particularly for indoor applications). Their are quite a few reasons for that, but you do need to be rather confident with camera / lens set ups, to get away with it. If in doubt stick to 'auto iris' lenses (I would imagine the majority would go with this latter suggestion). Secondly, setting up exposure control on a lens, is not really a problem. Dark on a test bench, is pretty much the same as dark up a ladder. As long as the threshold for iris control is set correctly on a bench, and then tested out of a window from sky to almost dark conditions, it should work anywhere. If you're really confident, you should be able to set the lens focus as well! A little tip for you (just don't tell anyone - it's a trade secret!) - if you want to set the lens focus on a camera which has yet to be installed into a housing which is already in place, simply wind a rubber band once around the lens body and focus ring, after it has been correctly adjusted; then the ring won't move. If you need to readjust at a later date, it's much easier to roll a band off the focus ring with your finger, then try and pick off a tape, particularly when you're 25 feet up a ladder in a force eight gale! If you use tape, it tends to get very sticky particularly if you need to readjust the lens some time later.

The simplest and cheapest thing to do (certainly to confirm whether it is an earth loop) is to 'insulate' the cameras from any contact with external metal. Maybe the first thing to try is, detach all the P.V. cameras from any physical contact with metal, and see if the problem has disappeared. I don't know these cameras, so forgive me if my guesses are wide of the mark. If the cameras have metal cases, or a metal retaining bolt is going into the internal chassis, and making contact with either a metal or grounded plate, or the housing itself, consider how to place an insulating barrier between the camera and whatever it's touching. Something as simple as a thick PVC tape (or lane marking tape) as a cushion, then maybe use heavy duty nylon cable ties to secure the camera. If it works, you've avoided the cost of an "engineering" solution. Incidentally, being low voltage, there is no requirement to ground them here in the U.K. I would assume the rules are similar Stateside.

antdickens A few suggestions for you. Plug in just three cameras which are powered from the same 12v supply. Hopefully you shouldn't see the problem. (By the way, I'm assuming that the "plugging everything into the same circuit" suggests all three Power Supplies connected to the same AC mains point?). If you do see the problem immediately, remove the first three, then try two or three cameras powered from one of the other PSU's. When you have a clear picture with 3 connected, start to add extra cameras - at some point the problem will appear. If it appears with camera 4, remove the cable, and sequentially try each of the others to confirm the problem. If you are able to connect 5 or 6 or 7 without the bands showing, that may indicate just a single camera providing the source of the problem. If any additional camera plugged in to channel 4 creates the problem, that indicates a power supply issue (albeit that there may be nothing physically wrong with the PSU). Should you be able to plug in 5 or 6 cameras before the problem appears, that may suggest a specific PSU is the source of the problem (swap the units over to confirm, or provide a replacement). If the problem still exists and you haven't managed to trace it, you'll need to post some more detailed info. on the general appearance of the 'faint bands', cameras, transmission (particularly cable paths), etc. Wish you luck!

Hi ccolvard Interesting little problem you have there. Here's a few 'if's' to be going on with.... If you have a battery powered test monitor, have you checked the picture straight out of the Pro-Video cameras? Picture o.k. or not? If not, you have a local problem, perhaps with the cameras (or power supply units). If the pictures are o.k., check the image quality at the other end of the camera cable, again using a battery test monitor. If the problem appears, it's probably down to a signal transmission issue. If it doesn't, connect the camera signal directly to a mains powered monitor (or TV with video input). If the problem appears, it's almost certainly an Earth (ground) loop hum, but almost certainly nothing to do with 12v DC. I don't know the cameras you're using, but if the camera case / weatherproof housing are metal, what are they bolted on to? If any part of the camera/ housing (and that includes mounting bolts or screws) is in contact with a metal clad building (for example), that can set up a problem. Maybe you could do a few more tests, and in the meantime, no doubt other guys will be along with some more suggestions.

Strewth, Talk about ironic; everyone wants to come to the UK, and practically everyone I know would like to leave Funny old world isn't it? Talk to most people over here, and they'll say that life has changed substantially over the last few years .... and not for the better. Petrol (Gas) is equivalent to about $7 (US) for a gallon (Imperial), parking is $ 6-7 per hour, a basic one bedroom flat (apartment) in London averages around $ 375k, crime is reportedly going down, but I've never personally come across so many friends and family being affected by crime in just one year (last count it was 11 people); hospitals are in crisis (allegedly), and that's just the good stuff! Rory, I'll have a look around and see if I can suggest any sites worth a look (it may take a day or two). Be prepared though, the 'old boy' network is alive and well and kicking here too. It's often not what you know, but who you know that counts. The last time I missed out on a really big consultancy contract, I was told that 'bulls**t beats brains'! You never know, others on the forum may have need for your talents DVR Expert Australia And I always thought that Australia was the land of opportunity! If you've got expensive habits, your going to need some serious dosh (money) to keep yourself smiling here. Mind you, you don't have to go too far to find a few Man. U supporters. Oh by the way, CCTV - just thought I'd mention it as I seem to have been lead astray somewhat.

DVR Expert Australia When are you planning on opening your U.K. branch?

When it comes to choosing weatherproof camera housings, the subject could probably fill a book on its own. Assuming that the camera is fitted with a fixed (small) lens, then a hinged housing is an advantage for the installation / service engineer, as there is one less piece of dropable stuff to worry about when you're up a ladder! Mind you, if you've never had a hinged housing fall back on your fingers whilst you're twenty feet up a ladder, you simply haven't lived! The main longterm problem with housings (apart from heater failure which is expected), is that various models can leak through the seals over a period of time. Top cover housings generally are the most water resistant, but there are one or two models I've seen in the past where the neoprene contracts with age, and you end up with the lens paddling in a shallow heated jacuzzi!! The problem of condensation on the inside of the glass is simply down to two factors; the temperature gradient between the air either side of the glass, and the moisture content of the air inside the housing. The larger the housing, the more damp air there will be inside. If the housing is small and well sealed you can pack some fresh silica gel in to absorb most of the moisture. Small 'comfortable' housings are not recommended in hot climates - you just end up cooking the camera! Apart from using a thermostatically controlled heating device to clear condensation, you can also use a very small fan directed onto the glass. Condensation will not form in a draught! It's actually quite rare to need an external screen wiper (and wash bottle) for a fixed camera. Generally speaking, the more horizontal the camera, the greater the amount of muck that will stick to the glass, so the more often it needs the loving attention of a friendly window cleaner. Just a thought but I'm not sure what this has to do with 'General Digital'?

546.8 yards baywatch, but whats a few feet between friends ( 1 metre = 39.37 inches) I'm sure we've done this one before, not that long ago!

Steady on rory, poor old vitaly has only just joined this forum. I always thought if a company supplies trade customers, then it's not unreasonable for them to describe their operation as a product distributor. Mind you, there does seem to be a different interpretation depending on which country you look at. Distributors in the UK are generally taken to be 'trade' only, whereas elsewhere some distributors supply to anyone. Hey guys, what's the situation in other countries?

Ooops Sorry guys, that should have been 550 yards. My brain still hasn't dried out from last weeks storms!

It's just under 550 feet rory. I'm not absolutely sure, but I think their may be a slight difference in interpretation here. Rory, I think your talking about how to transmit a signal over 500 metres, whereas, Daranijo, I think you're talking about either viewing objects 500 metres from the camera, or perhaps covering 500 metres width on screen. Perhaps you could explain in a little more detail what it is you are trying to do, and then others can offer their suggestions. Thanks.

I like the thinking behind your logic, but unfortunately it doesn't quite work like that. As an example, if you imagine a full screen camera image which clearly shows the '470 line' resolution bars on a test chart, if you then squash (compress) that image down to 1/4 of its original size, you can no longer resolve those same bars. As I recall, with a quad unit, the output resolution of a full screen image (comprising 4 quad pictures) will overall be the maximum resolution supported by the digital memory / frame store. So whether you use 600 line B&W cameras or 330 line colour models, the limiting factor on output resolution, is never likely to be much better than perhaps 500+ lines over the entire image. It does make some difference if you use top quality cameras; the individual quadrants undoubtedly look better, but you will always be limited by the quality of the compression / storage circuitry. Perhaps another way of looking at it is, if you have a VGA picture divided into four on a computer monitor, each quadrants resolution will be 1/4 VGA. I think I'm waffling now ... time to shut up

kdberg I don't claim to be up to date on all the latest 'quads' on the market, but I certainly can't think of any that have a frame store capable of supporting that resolution (at least not in the CCTV industry). Unless anyone knows of a suitable unit, it's possible that you may find something in the Broadcast sector, but that's going to be big bucks. I'm not really sure why you need to go so far up spec on a unit if you're using 470 line cameras. Any top end 'quad' is going to produce a very acceptable image for most applications. Just a couple of other thoughts; If you're splitting the signal off to three points each a few hundred feet away, you may want to use a good quality Video Distribution Amp. to maintain the signal levels. If the first is a few hundred feet, and the other two are in close proximity, you could simply use a higher grade cable, and looping outputs, without the VDA. Also, depending on the size of the displays, if it's anything less than 17", I would be tempted to go for a flat panel LCD, rather than a conventional CRT model. The 800 lines centre resolution will drop off (towards the edges) on a CRT, and if the display is a permanent quad, the tube will burn in very quickly. With an LCD neither of these problems apply. If you'd already thought of this, apologies for stating the obvious.

That's probably why I never made any money out of my installs, all those years ago

Hi Thomas, Maths was never my strong point, but your focal length figure for the 1/3" example looks pretty near spot on. 2/3" er, not quite. 50metres width coverage at 200 metres distance should be approx. 18mm for 1/3", and 35mm for 2/3". The answer to your question is simply that imager size is always going to be a crucial factor when considering the field of view. But it's perhaps better to look at the problem from the other direction. If you standardise on a format for most work, for arguments sake 1/3", then you have a vast array of optics available, which will cover most projects (obviously assuming the camera has an interchangeable lens mount!). To maintain the same width coverage (field of view), as the imager gets larger, so the focal length must become longer. 25mm on 1" is the same as 12.5mm on 1/2", 16mm on 2/3" is the equivalent of 8mm on 1/3" (they are all 'standard' lenses).

...and the mare hanging on till it arrives. You often find that when you go to install the camera, that's when you notice a small four legged friend that wasn't there before Bottom line is, as long as it does what you want, that's really all that matters (and you have a nice cute healthy little beastie, with a good natured mother to help). Hope it all goes well, and keep us posted.

Spot on Rory!! I should have looked at the dimensions for the final clue. It certainly looks like a bullet camera on paper. creekside, The obvious problem you'd have using a 'bullet' camera, is you're generally stuck with the lens it comes with. The type of camera I had in mind (although we don't consider Ganz a major player this side of the pond, and I've absolutely no experience of using it, or indeed its retail price) is at:- http://www.cbcamerica.com/cctvprod/ganz/cams/csmount/csindex.html Any equivalent quality brand would work a treat. If you're only going to use the camera for a short period, you won't need a housing, provided you leave the camera powered up all the time. If you don't need to use it, take it down and pack it away for the next season. A little clue for you - if it gets colder, she may well hang on, and if it warms up, then things may happen faster than you expect. Get that camera in quick, or it's no sleep for you this fall.