Page "Operation Igloo White" Paragraph 15

The sensors reported their data via radio frequency channels ranging upward from 162. 5 megahertz ( MHz ) to 133. 5 MHz on the very high frequency band.

31 channels were assigned to each type of sensor with a 375 kHz separation between each channel.

Every channel contained 27 identification codes or addresses which could be set in the field prior to emplacement.

Thus, a total of 837 individual sensors ( 27x31 ) could be deployed at any one time without signal duplication in a single operational zone.