A Car Identity Comb

This device is as simple as it could be. It consists of a comb stamped out of sheet steel and fixed in a sealed void within a car's (or any other object's) structure.

 The comb's teeth are of varying lengths. The selection of lengths is
chosen in advance to be different from all other similar combs.

Each tooth of the comb will vibrate to some degree when excited by a vibration stimulus. A detector designed to receive the vibrations from all the teeth of the comb at once can convert the vibration frequencies received into an indentification number.

A typical comb would be around 6 centimetres long from the fixing edge to the end of the longest tooth. The maximum tooth length would be around 4 centimetres and the shortest around 2 centimetres. If the tooth lengths are stepped at one millimetre intervals, 21 different tooth lengths are possible. A typical comb would have 12 teeth. With 21 different lengths and 12 teeth, more than 100 billion combinations are possible.

A car could be fitted with two or more combs so that at least one comb would be left undamaged in the event of an accident. In the event that a car had been constructed from two cars that were written off, using the front half of one and the back half of another, the identity combs would show that parts of two cars were used.

The identity comb can be set into vibration by a gentle tap on the car's bodywork near where the comb is located. Typically this would be near a strengthened part near a jacking point. The gentle tap could be administered by the detector unit. A contact microphone in the detector will pick up the vibrations from the comb and provide an electrical signal for further processing.

The musical notes produced by the vibrations of the comb's teeth can be separated and identified by a spectrum analyser. The note combination is then digitised for storage in a memory unit.

A typical compact disc could hold more than 100 million identification numbers. If a compact disc drive is incorporated in the detector unit, the unit could detect a car's identity within a few seconds. New compact discs are easy and cheap to produce so frequent updating is no problem.

The identity comb has the advantage that it cannot be removed from a car's structure without causing major damage. If two or more combs are fitted in a car when it is manufactured, removal of one set of combs and replacement by another set would be uneconomic for any car thief. A car with no combs or with unknown comb numbers would be instantly identifiable as having been stolen. It is a simple matter to arrange that combs are allocated to cars in a random series and the comb number fitted to a car is recorded with the chassis and engine numbers. The combination of numbers would make forgery of a set of numbers almost impossible.

The vibrations of a comb's teeth caused by a car's movement will make the whole car's body vibrate a minute amount. These vibrations may be detectable remotely by the use of a laser. If this can be made to work, all cars passing a detection station could be identified automatically. A network of detection stations could then be used to locate stolen cars very quickly. Detection stations at ports could foil attempts to import or export stolen cars

Originally designed in April 1993. An attempt to get a working patent then did not get very far.

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