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Remember when camera multiplexers used to be exotic, complicated, difficult to use and eye-wateringly expensive? Not any more, this 16-channel unit from Dennard costs only slightly more than a mid-range colour camera!



As colour camera multiplexers go the Dennard CPX1600 isn't much to look at however the old adage about not judging a book by its covers certainly holds true in this case. The first surprise is that it is a 16-channel design, though from the number of buttons on the sloping control panel you would never guess. The second revelation is the price; at less than £500 it puts serious camera multiplexing within reach of a much wider market.


The specification is fairly modest but it has all of the essentials. In addition to 16-channel simplex multiplexing the CPX1600 has two independent monitor outputs, AGC correction is applied to each camera input and there's a choice of full frame or quad display during playback. Each monitor can display an independent live camera sequence, the unit supports real time or time-lapse recording, (up to 960 hours) and there's a facility for to detect tape end and trigger an internal alarm. 


Dennard has obviously managed to save a few bob on the casework; the CPX1600 is housed in a nondescript all-steel sloping console. A simple membrane keypad covers most of the top panel but even though the designers have spread the 13 'buttons' out to fill up the space it still looks empty, almost unfinished, as if there's going to be a Mark II version. A single two-digit 7-segment display and a handful of status LEDs are the only visible indications that it is powered up and working. The buttons are arranged in three distinct groups, the four buttons in the top left hand corner handle camera selection (more about that in a moment), on the right side five buttons are for function shift, time-lapse mode, playback display, direct VCR recording and alarm cancel. Four buttons in the bottom left corner are used for quad display, auto sequence on/off and the two monitor selector keys.


Normally on a 16-channel multiplexer you would expect to see a row of 16 camera selector buttons but once again Dennard has defied convention by combining the cameras into groups of four. That makes manual camera selection slightly slower than it would be on a switcher/multiplexer with individual camera selectors. In order to access camera 4, for example, button 1 (cameras 1-4) would have to be pressed up to three times.


The rear panel is more conventional, there are two rows of BNC sockets, and the lower 16 are for the camera inputs. The first 8 sockets on the upper row are loop-throughs for cameras 1 to 8, next to that are the VCR input and output connectors, followed by the two monitor outputs and lastly two sockets for VCR camera switching (or 'stepin') and the alarm output. The only other features are a 16-way mini DIP switch for setting camera termination and two slide switches, one for locking the front panel controls, the other for switching the alarm function on and off. The unit is mains powered and the cable socket is on the far left, there is no on/off switch.


Inside the case there's not a lot to see. A large PCB, mostly populated by dedicated microchips and surface mount components is responsible for all of the vision processing, next to that is the power supply module and there are small PCBs on the rear panel for all of the input and output connections. The standard of construction is generally very good and since there are no mechanical parts to speak of it should enjoy a long and healthy life.


The initial set up will take the average installer around ten seconds! There are no time or date adjustments to worry about, no displays at all in fact and only a couple of switchable/programmable functions. At switch on the unit scans the active camera inputs, adjusting the AGC for a normalised 1-volt p-p. During the power-up routine the multiplexer also gives a relative indication of input signal strength by flashing a sequence of LEDs at the same time as the camera number.


The two switches on the back panel enable or disable the alarm functions and keyboard lock, the termination switches are normally left in the on position (unless any of the camera loop-throughs are used). The two programmable functions are camera sequence -- connected cameras can be locked out of the sequence -- and the dwell time can be set (the default is 4 seconds). This is a global adjustment for all cameras; individual dwell times cannot be varied. Each action is accompanied by a rather sorry sounding squeak, if nothing else Dennard must do something about the bleeper…



The multiplexer defaults to the record mode, pressing the 'auto' button starts the sequencer. The picture is briefly blanked during the switching interval to prevent picture roll, it is a bit disconcerting but the image remains reasonably stable.  Manual camera switching, despite the lack of individual selector buttons, is no great hardship, though until you get used to it, it does require a few moments extra thought to work out which button to press, and how many times. The absence of any on-screen displays is arguably the biggest operational problem. It's just about liveable on a basic 4 or even 8 camera system but on a 16-camera set-up it is important to have clear on-screen idents and preferably time and date information as well, more so when the system is used in conjunction with a VCR. 


Function switching is obviously very straightforward as well and the unit responds quickly to a video loss; switching continues with the missing camera omitted from the sequence. To view a recording it is necessary to press and hold the Play button on the multiplexer for two seconds, camera channels are tagged so each one can be viewed singly by pressing the appropriate selector button, or four at a time using the quad display.



Live video passes though to the monitor display with little or no discernible reduction in resolution, changes in colour fidelity or any increase in noise, in short the unit is pretty well transparent to video. The quality of recorded video playback depends almost entirely on the performance of the recording medium, using a standard VHS machine there is the inevitable increase in noise and loss of detail but the CPX1600 doesn't add to the degradation. Apart from that the only noticeable difference between live and recorded video is the reduction in frame rate, which varies according to the number of cameras connected. Camera switching during replay is clean though the auto sequence function is disabled. The quad display is also clean and stable with acceptable (and expected) reductions in the amount of detail and colour depth.



It might seem churlish to make too many criticisms about such a competitively priced product but the CPX1600 does have a couple of fairly significant flaws. The biggest one has to be the lack of any on-screen idents or displays and that could impose limitations on the type of cameras and recording equipment it can be partnered with. The other, less problematic concern is the annoying flashing blank screen during the switching interval. It only lasts for around a quarter of a second but if the unit is going to be used for real-time observation, as well as multiplexing, we suspect some operators may find it difficult to live with. Unfortunately there is no option to display a quad image during record/live mode, which would have solved the problem. The third and last quibble is the lack of flexibility for setting individual camera dwell times. It's not a very pretty sight -- some effort could be made to improve the cosmetics -- but we'll overlook than and we don't go much on the squeaky bleeper, on the other hand it does grab your attention… 


On the plus side there is video performance, it is very good indeed with no significant reduction in quality or loss of detail after the signals have been through the digital-processing mill. It is also very easy to install, set-up and use and last but not least, the price is remarkable for a 16-channel multiplexer. If the CPX1600 is going to be used solely for camera multiplexing, and the VCR or cameras can supply date, time and, if necessary, ident info then it scores high marks all round. In a simple camera-switching role it has its limitations, though they're certainly not serious enough to rule it out.  




Power supply              230 VAC 50Hz

Weight                        4.5kg

Dimensions                 440 x 95 x 230 mm





Product design 8

Build quality               9

Ruggedness                9



General functions            8

CCTV functions            8         

Ease of use                 9

Instructions                8

Manuf. support                                   



Video quality              9

Switching                    8

Audio                          n/a


Ó R. Maybury 1999 0104



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