WHAT OUR EXPERTS SAY...
When it comes down to it, it doesn’t matter
how good a CCTV camera is at resolving fine detail, or seeing in poor light. If
no one is actually looking at the monitor, or the output isn’t being recorded
when a critical event is taking place, then it might as well be switched
Where a camera is being used to monitor a
predominantly static scene the traditional solution is to associate it with
some sort of detection system, that will trigger an alarm, enable a recording
device or alert an operator. However, that means extra hardware, a more complex
installation, greater expense, and more to go wrong.
So why not use the camera image to detect
movement? It’s a classic example of lateral thinking that has spawned a wide
variety of devices and systems.
Nowadays even cameras are equipped with built-in motion detecting
facilities, but few, if any solutions are as quick and simple to install as the
Primary Image Video Tracker.
Video Tracker is available in two basic
versions, as a stand-alone product or in rack-mount casings. We’ve been looking
at the stand-alone variant. It is housed in an innocuous-looking black box,
formed from extruded alloy, measuring 110 x 165 x 33mm. At one end there’s
three BNC sockets, labelled video in, video out and track display. There’s a
pair of red and green LEDs, and two miniature rotary switches. At the other end
there is a bank of screw contacts, two 10-pin connectors, and a DC power
socket. The multi-pin sockets are used to connect two or more Trackers
together, to form a simple network, and for external control of several
additional functions, via a PC; more about that in a moment. Video Tracker is
powered by a plug-top mounted 9 volt DC mains adaptor that is supplied with the
Inside the box there’s a single glass-fibre
PCB, smothered in chips and surface-mount components. It seems likely the two
LSI (large scale integration) chips are responsible for all the video
processing, though we’ll have to take that as read as their identity has been
obscured, with a grinding wheel! Other components of note include a
non-volatile memory, an EPROM, (erasable programmable read only memory) which
is a removable and hence upgradable, memory chip containing the system’s
operating software, and a small sealed relay.
So how does it all work? Installation couldn’t be much simpler. The
output from a camera connects to the Video Input socket and the Video Output
loops the video signal through to the monitor, switcher, recording device or
wherever else it was going, before Tracker was fitted. The Track Display output
can be fed to a separate monitor, it shows a superimposed activity display,
with a white rectangle surrounding the moving object, (or objects) for 5
seconds, as it moves around the scene area. One of the two rotary switches on
the front of the unit controls sensitivity. It can be varied in 16 steps, to
respond to objects that vary from 2% to 12% of the total screen height. The
movement-sensing software has been configured to be most responsive to a
standing human figure. The second rotary switch is used to enable or blank the
Track Display video output. When disabled the image comes back on for 20
seconds, after movement has been detected.
The initial set-up for the basic stand-alone
unit is a matter of trial and error, depending on the scene, but the factory
default setting is a good place to start. The alarm relay is wired up to the
bank of screw terminals on the rear of the unit, with connections for common,
normally-open (NO) and normally-closed (NC) contacts. The terminal also
includes a 9-volt DC source, which can be used with the relay terminals if
When powered up Video Tracker goes through a
short self-test routine that takes approximately four seconds, after which the
green LED indicates the unit is ready. When motion is detected the red LED
lights up and the relay is activated, for the duration of the event, relay
dwell time is factory set for 2 seconds.
If required Video Tracker can be supplied
with several additional functions; they can also be enabled after purchase, for
what Primary Image say is a minimal extra cost (£90...). The key feature is
zone masking, additionally there’s relay dwell time adjustment and alarm
configuration. Zone masking is a fairly basic facility in video motion
detection as it allows areas of the picture – where non-critical activity or
movement may be expected -- can be de-selected.
Another option worth mentioning is the
facility to drive a PTZ head, to automatically follow movement. At the moment
the system is only compatible with specified Videmech models. Primary Image can
supply full details of the data and control protocols so it should be possible
to use it with other systems. PTZ steering software can be supplied as an
option and is priced at £45.
Video Tracker communicates with the PC or
terminal, using terminal emulation software, via a standard serial interface.
The cable and set-up kit is yet another option, this time costing a further
£45. The extra functions are controlled from a simple menu-driven display. Menu
Z covers zone mask set-up. The mask outline is defined by a moving cursor,
controlled by the numeric keypad. Once set it is stored in Tracker’s
non-volatile memory. Menu A covers the alarms, the options include enabling or
disabling all alarms, set relay dwell time and display current alarm status.
Menu D overrides Tracker’s display blanking function. Menu O overrides the
unit’s sensitivity setting, and Menu L is used to enter a licence key code,
needed to enable the additional features if they were not specified at the time
The video through port appears to be
completely transparent to the incoming video signal, in other words fitting a
Video Tracker to an existing system should have no impact on performance.
We tried the unit with several different
makes and types of camera. It was most sensitive when used with a monochrome
camera. This was almost certainly due to the fact that B&W cameras produce
a more contrasty image under a wider range of lighting conditions. Nevertheless, it worked admirably well with
properly set-up colour cameras, viewing well lit scenes. The sensitivity range
is more than adequate to mask out the effects of small movements – wind-blown
branches or plants and small animals – but we suspect the very useful zone mask
facility is likely to be required in a lot of installations.
The first point
to make is that Video Tracker is a relatively expensive device. Cameras with
built-in motion sensing facilities are now becoming available within in the
same price bracket. Admittedly the alarm functions on most of those cameras are
not as straightforward or as easy to use as Video Tracker, but for how much
longer? Furthermore, the cost of adding on or enabling what we regard as a
basic motion sensing facility – namely the zone mask – does seem rather high.
On the plus side the basic set up is very easy and it has no effect on the
normal operation of other components with a system. The alarm function is
flexible and there should be no problems integrating it with other equipment.
Video Tracker is a potentially very worthwhile enhancement or upgrade for
existing CCTV systems, and a useful way of adding in extra functionality to new
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 1998 2702