The signal attenuation of “Datastop” Glass is achieved by the use of several layers of specially developed coatings which are effective in the electric field by reflection of the signal. The attenuation provided will depend on the characteristics of the signal, and the electrical connection at the glass edge.
The unit of attenuation is a logarithmic one, the decibel (db). The graph in Figure #1, shows the relationship between decibels and the percentage attenuation (reduction) in the electric field.
The attenuation performance was measured using a test sample of aproximately 1m² inserted in the wall of a 2.5m cube screened room for frequencies up to 1GHz (1000 MHz). For frequencies above 1GHz a 1 metre cube screened enclosure was used.
This method is based on the specification in US Military Standard MIL-STD-285C and consists of measuring the transmission between two aerials 2 metres apart. The attenuation of the glass is measured by comparing the transmission through the glass when glazed in the screened room, with the signal strength in open field conditions. (See Figure #2)