COMPUTAR CPLEX 16M VISION MULTIPLEXER
WHAT OUR EXPERTS SAY....
The dramatic effect vision multiplexing has
had on multi-camera surveillance is often overlooked and the facility to record
the outputs of several cameras on a single time-lapse VCR is now taken more or
less for granted. However, the technology required to accomplish this feat --
once only viable on critical, cost-no-object installations -- is now available
to a much wider market, thanks mainly to the significant cost reductions in
digital video processing microchips.
The Computar CPLEX 16M multiplexer clearly
illustrates the progress that has been made in this field. It is manufactured
in the US by Robot Research Inc., who have been responsible for much of the pioneering
development work in vision multiplexing. This model is very clearly related to several
models in their Optima range, the main difference being this one is designed
for monochrome cameras, moreover it has a slightly truncated range of features.
Externally the unit is quite compact, it is
housed inside a slim, black metal case measuring 432 x 311 x 44mm. On the front
panel there are five groups of button with mode and function keys on the left
side, and the camera selector buttons on the right. The back panel is populated
by two rows of BNC connectors for camera inputs and outputs, a single monitor
output, one DB25-S connector for alarm inputs and outputs, and a socket for the
external mains power supply.
Up to 16 cameras can be connected to the multiplexer;
they can be any type having a CCIR/PAL output. Unlike first-generation
multiplexers there’s no need for external synchronisation or genlocking, this
is carried out internally. However, one of the most important features on this
device is dynamic time-division (DTD). This varies the amount of time each
camera output is allocated for recording, according to whether or not there’s
any movement in the scene. This makes the most efficient use of a recording
VCR, ensuring that critical areas or events receive the most coverage.
Each camera input has it’s own programmable
motion sensor facility. This takes the form of a grid of 192 targets (12 x 16),
that can be switched on or off, to concentrate on a particular area, or areas
within the scene. When movement is detected the multiplexer creates a ‘motion group’,
where the output from the camera (or cameras) are repeatedly inserted into the
recording sequence, so they’re recorded more often.
There are four display formats, selected
automatically by the multiplexer, according to how many cameras are connected.
In addition to a single camera output the screen can show 4, (2x2), 9 (3x3) or
16 (4x4) images, either live from the connected cameras, or on playback from a
VCR recording. Incidentally, this is a simplex design, so recording and
playback functions cannot be carried out at the same time. A built-in character
generator superimposes time, date, video loss, alarm status and camera idents,
which can be up to 10 characters long. The initial set-up and routine operations
are controlled by a series of menu-driven on-screen displays, protected against accidental or unauthorised
alteration by a control lockout function.
An alarm input is assigned to each camera; contact
closure whilst the unit is in the record mode results in the associated camera
indicator flashing and the image displayed on the monitor, along with a superimposed
alarm message. An alarm indication is recorded on the tape, and the VCR output
switches to alarm mode, with the relevant camera prioritised. Alternatively, if
the unit is in ‘1-cam’ mode, only the alarm camera will be recorded. During
playback the multiplexer responds to recorded alarm indications by flashing the
appropriate camera indicator on the front panel and overlays an alarm message
on the screen. The system detects and responds to the loss of a video input in
a similar manner.
SET-UP AND OPERATION
The main set-up menu is accessed by pressing
the function and sequence buttons together. This brings up the time/date
screen; the following pages cover housekeeping functions for the various display
and alarm options, VCR and alarm record times, alarm duration (2-999 seconds),
camera dwell time (1-99 seconds), camera titles and set-up screens for the 16
motion detector grids.
On the motion detector display all of the
targets are enabled by default, they are switched off using the camera selector
buttons, a line at a time, until the area to be covered has been defined. Unlike
some other models in the range the CPLEX 16M’s motion detector doesn’t have a separate
alarm output, nor are there any indications that it has been activated.
In spite of all the heavyweight digital
processing taking place image quality is surprisingly good. Very little
additional noise is evident on a ‘live’ full screen display, nor is there any
significant loss of resolution or detail. The dynamic range is slightly
narrower than a purely analogue signal but it has little impact on image
quality; in practice the recording VCR
will usually have a far more detrimental effect.
The quality of multiplexed images is reduced slightly
though with a very small reduction in detail and increase in noise though the
effects are only really noticeable on test patterns.
Robot’s wealth of experience and expertise in
this area are clearly evident on the CPLEX 16M. Construction, design and layout
are of a very high standard, and performance is hard to fault. From the
installers point of view flexibility and the ease with which it can be
incorporated into existing systems are important assets moreover dynamic time
division and motion detection are two key facilities, that give this device a
significant advantage over most other multiplexers on 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 1996 2604