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These days there’s no shortage of well specified colour, quad-display multiplexers available to installers and specifiers. In contrast there are comparatively few monochrome models to choose between. Clearly the falling cost of colour cameras is one reason for the market bias, but it’s easy to overlook the fact that the majority of surveillance cameras and systems remain firmly entrenched in monochrome technology. There is a still a very healthy demand for black and white peripherals and ancillaries however, something that Robot UK have sought to address with the new Appro MPX 9104 multiplexer.


The price is remarkably competitive, though the specification is by no means basic. Up to four inputs can be combined, for simultaneous display and recording. It has a range of live display modes, including quad and single camera. Duplex operation means it can record, and display images at the same time. A built-in character generator and clock displays the time and an ident for each channel. Alarm facilities include video loss and contact closure sensing for each channel. It has four programmable motion detectors, one for each input, these are used for alarm activation or activity detection. Alarm events are signalled by an on-board bleeper. The display has a resolution of 1024 x 512 pixels, with 256 greyscales, and all camera synchronisation is carried out internally.


The Taiwanese-built MPX-9104 is housed in a cream-coloured, standard 19-inch rack mountable case measuring 420 x 200 x 44.4mm. There are only eight buttons on the front panel, each with an indicator LED. The first three, ‘Select’ ,‘VCR’ and ‘Sequence’, have dual functions, firstly to set the display position during VCR replay, switch to VCR replay mode and engage auto sequencing. They’re also used to enter the set-up mode, and control various functions on the on-screen displays, which we’ll come to momentarily. The next button is for switching between the quad and full-screen display mode; the four remaining buttons are for channel selection and cursor control for the menu functions.


Around the back, on the back panel, there are 11 BNC sockets; 8 of them are for the four video inputs and their associated loop-through outputs, the other three are for the monitor output, VCR input and output. Next to each video inputs there’s a rotary gain control with a range of +/-2dB; the video output is unaffected. There are two 9-pin D-Sub connectors; the upper one is for a remote control operation, using an optional RC-5004 keypad, or via PC, using RS-232 serial communication link. The lower one is for the external alarm inputs, with provision for normally open or closed contacts. Also on the back panel is the main on/off switch and a socket for the external 24 volt mains adaptor.  



Pressing the select and VCR buttons simultaneously brings up the first of five pages in the menu display. This covers setting camera title or ident, video loss alarm enable/disable, dwell time (0 to 99 seconds), video output (live or multiplex), time and date setting and display mode. The second menu page deals with alarm settings. This includes sensor type (N/O or N/C) and sensitivity, alarm hold and duration, VCR type, operating mode and record time. Menu page 3 is concerned with the device ID code and control lock, RS-232 configuration, bleeper enable/disable, relay output and video motion detector set-up for each channel. The latter, when selected, displays a matrix 12 x 24 targets. The area of sensitivity is defined by switching targets on or off as required. Sensitivity can be set in a range 0 to 99. The final menu page is an alarm activity log, that lists the last 64 alarm events, along with time, date and type of activation.


When a video loss or external alarm is triggered the unit responds by sounding the bleeper, the corresponding channel LED indicator starts to flash and a warning message appears on the video display. The last image is frozen, in the case of video loss. If the motion detection system is triggered the word ‘motion’ appears on the screen and the sequencer increases the repetition rate of the associated channel in the VCR output.  


The instructions contain all of the information an installer is likely to want or need. They’re fairly well-written too, and mostly easy to follow. The set-up routines are reasonably simple; accessing some functions can be quite time-consuming, however,  since they’re only likely to be set once, following installation, it’s not a major problem.



Image quality is very good indeed. Evidence of the  heavy-duty digital video processing going on behind the scenes is evident in the jerky motion artefacts on full and quad-screen displays but resolution remains impressively high. There is some loss of detail and the contrast range is narrower but it is negligible, compared with the losses that occur when the image is recorded to tape. They’re virtually undetectable when compared with an un-processed off-tape recording of the same scene. Camera switching is very clean with no disturbance at the switching point.   

Replay of multiplexed recording is very clean, though much depends on the capabilities of the VCR.


The motion detector system is most efficient, though it can take some time to get the correct sensitivity level, especially on an outdoor scene. The audible alarm is rather quiet though. If an external sounder isn’t used it could go unnoticed in a noisy control room, though the on-screen and front-panel indicators should ensure an activation will not go unnoticed for long.  



The designers have struck a very good balance between features, performance and cost. The MPX-9104 works extremely well. We don’t anticipate any problems with installation or set-up, and once programmed it requires very little operator attention. A useful piece of kit that fills a noticeable gap in the market.



Design and design features              ****

Circuitry and components                  *****

Ease of installation and wiring    *****  

Range and variety of functions            ****    

Accompanying instructions                   ****                             

Technical advice and backup            ****     

Value for money                         *****                          



Ó R.Maybury 1997 1509



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