The Dräger Interlock XT comprises two main components: the breath-alcohol measuring instrument with the measuring system, which is situated inside the vehicle, and the control unit which is generally installed under the dashboard and allows or prevents current being supplied to the vehicle's starter system.

When the ignition is switched on, the Dräger Interlock XT requests a breath sample from the driver. The result of the breath-alcohol concentration measurement determines whether the vehicle's starter is released and the engine can be started.

Car drivers find long waits after switching on the ignition particularly annoying. Therefore, during development of the Dräger Interlock XT, particular attention was paid to ensuring that the instrument would be ready for use quickly.
Because the Dräger Interlock XT even works perfectly at -45 °C (during the Scandinavian winter, for example) and at 85 °C (in blazing sunlight, for example), it was given the name "XT", for "eXtended Temperature".

The Dräger Interlock XT determines the breath alcohol concentration by means of an electrochemical sensor system, as it is used also in breath-alcohol measuring instruments of police authorities. It reacts with high specificity to alcohol. As a result, other exhaled substances do not distort the measurement result.

While the vehicle is in use, all relevant events are recorded in the Dräger Interlock XT's data log: date, time, submission of or refusal to submit a breath sample, measured alcohol concentration, engine starts and stops, electrical bypassing of the Interlock and any other attempts to tamper with the device. The data can be downloaded and compiled in a data record.

The use of auxiliary means to circumvent the Dräger Interlock XT, as for example an air pump, is reliably detected and starting the motor is prevented.

Dräger is world market leader in breath alcohol measurement. The Alcotest® family of products is the most successful breath alcohol measuring instrument world-wide. The well known Alcotest tube with the sample bag is probably the oldest method of obtaining proof of alcohol consumption. Today, most alcohol detection devices are electronic. They are used on all five continents for traffic safety by police authorities, for workplace alcohol testing, as well as aiding in the diagnosis of medical patients.
Dräger’s long term experience and time proven measuring technique establishes the basis of the Dräger Interlock XT.