spread spectrum
A signal struc­turing tech­nique that employs direct se­quence, frequency hopping or a hybrid of these, which can be used for multiple access and/or multiple func­tions. This technique decreases the potential interfer­ence to other receivers while achieving privacy and increasing the immunity of spread spec­trum receivers to noise and interference. Spread spec­trum generally makes use of a sequential noise­&#8209;like signal structure to spread the normally narrow­band informa­tion signal over a relatively wide band of frequencies. The receiver corre­lates the signals to retrieve the origi­nal informa­tion signal (NTIA)
Normal scanners cannot get spread spectrum transmissions.