According to the regulations in Belgium a site that has a portal detector must do a system test when there was no alarm during 30 days. To be able to do this test without a radioactive test source we can install a test button on the detectors. With this test button it is possible to generate an alarm electronically.
This test button can be a normal push button or a key switch. By pushing the test button we generate electronically a number of pulses which generates the alarm in the detector. By doing this the required self-test has been done.