The rigging in the exam hall nowadays is applied in digital means. The recent development is to use a small credit card sized mobile phone and a Bluetooth-enabled ear-phone. The mobile and the earphones are connected by Bluetooth. A group of miscreants is involved to help the examinees to execute the rigging in exchange of a large amount of money from the individuals. The group collects the question papers during the exam, solves the question, and from a central location transmits the answers to the contacted examinees.

Professor S. M. Lutful Kabir of IICT, BUET, out of curiosity, investigated the devices and analyzed the problem. He gathered information on the detail use pattern of the digital rigging devices. It was discovered that the examinees carry the mobile in different places on his/her body, and the location is not fixed. However, the location of the earphone is fixed, and it is within the ear. So, Prof. Kabir targeted his investigations only to identify the ear-phone.

The earphone is a very small device having a length of 1 cm and a diameter of 0.6 cm. It contains a speaker, a small button battery, and a Bluetooth circuit. A biased magnetic field is applied to identify the possible presence of the device. When the created magnetic field approaches the device the metallic components in the ear-phone dislocate the field path and hence its strength. To identify such devices, the disturbance is measured and the measurement is used. A prototype of the detection instrument is made and tested on the rigging digital device; the result is found to be satisfactory. The instrument is practically demonstrated in the ministry on 21st March 2024.