2 February 1996

put em off

Best advice is to

With such a range and variety of security systems available, is there any excuse now for thefts of farm livestock, machinery, tools and equipment? Peter Hill outlines the different alert and deterrent systems on offer

ALTHOUGH the idea of setting a trap to catch a thief is appealing, deterrence is reckoned to be the more favourable route. There may be some satisfaction in seeing perpetrators caught in the act and swiftly clamped in irons. But by then, damage to property or stock may already been done.

The danger of making it obvious that premises are protected is that the professional thief will know how to get round them, or will at least make them more wary.

Common sense and professional advice are probably the best tools for arriving at the right answer for given situations. The former is down to the individual. There is no shortage of the latter given the huge industry which has grown on the rising wave of crime, a growing feeling of insecurity (particularly in many rural areas) and advances in electronics that produce ever more ingenious devices.

First task is to establish what needs to be protected and how those of a criminal persuasion might go about either damaging or getting their hands on it. Next, what is the most appropriate form of detection for the situation? Then, what is the most appropriate response – some form of deterrent or a remote alarm?

The accompanying table shows the principle options in each case. Infra-red detectors come in "fan" patterns for picking up movement within yards or open buildings, or as a narrow beam projected across farm roads and gateways. They can also be used three or four at a time to form an invisible barrier around a set of buildings, vehicles or machinery.

Radar, trip wires and highly sensitive microphones can also be used in a similar way, with magnetic trip switches activating an alarm or an alert signal when gates or doors are opened. In all cases, reliability is a key issue to discuss with suppliers – not so much that detectors will always work but whether they can be relied on not to set off false alarms.

Deterrents range from floodlights to electric shocks with wailing or screeching alarms, recordings of shouting voices or dogs barking and exploding fireworks in between. Automatic floodlights are probably the most commonly used deterrent because they are also convenient for those meant to be on premises in the dark rather than being particularly effective.

Professional thieves will tend to "case" a target beforehand. If they know it is a remote spot they may be more thankful for illumination instead of being put off by it.

Sirens are equally of questionable value in remote areas. They may provide an initial shock but hardened criminals who work fast know that response takes time – and alarms are so often ignored these days anyway.

One way of making such deterrents more successful, suggests Richard Sutcliffe of Sutcliffe Electronics, is to set up a system with time-delay switches so that lights and sirens are turned on in sequence. That introduces some uncertainty as to whether they have been triggered by the intruder or turned on by someone else.

The more offbeat deterrents, such as Martleys Doberman recording, would no doubt be effective in scaring off less-seasoned criminals. Likewise the "alarm mines" from AES Radionic, which are electrically-triggered pyrotechnics and go off with a loud bang and bright flash.

If the idea of being alerted to the presence of intruders is more appealing so that they can be challenged or have their means of escape blocked and the police called, then there is again no shortage of ideas as to how this can best be done.

The most common is to link infra-red beam detectors by wire or radio to an alert receiver or (by radio) to a personal pager. With the latter, alert alarms can be several miles away from the area being monitored.

The same is true of the radio alarm interface from Sentinel and AES Radionic, which connects detectors to personal communication radios.

The Field Monitor from Custom Electronics is similar in principle but different in execution. It uses a highly sensitive microphone as the detection device. This is set to accept the "average" background noise of its location and then trigger an audible or remote alarm when it detects significant changes in the noise level – from a vehicle, equipment or livestock being moved, for example.

At the receiver the noise is substantially amplified, acting not only as an alert but giving some idea of what is going on. Richard Robertson maintains the system often has greater detection range and scope than other methods.

The company also produces a multi-detector alarm or alert system for guarding equipment and premises in one locality. This can be used in conjunction with several stand-alone movement sensors tuned in to a central alarm unit providing extensive coverage at reasonable cost. &#42

Ripe pickings… Protection needs to be more than just a locked door.

A reasonably modern building but is it thief-proof? The correct type of detector needs to be chosen and, above all, it must be reliable. It is worth noting that professional thieves will tend to "case" a target before striking.