There are 4 major brands of radios - Futaba, Airtronics, JR/Spektrum, and Hitec. Of those the JR/Spectrum use DSM2 (Digital Spectrum Modulation) and the rest use FHSS (Frequency Hopping Spread Spektrum).

The DSM technology examines the spectrum of available frequencies when it is turned on and then chooses two of those frequencies for transmission on, the receiver gets these from the transmitter and those are what are used while in flight. If one frequency gets blocked then it can still transmit on the other frequency

The FHSS technology starts on a given frequency and then both the transmitter and receiver start "hopping" to another frequency every 40 milliseconds. If that frequency that is hopped to is being used it won't hurt the radio as it will move to the next frequency in 40 milliseconds. The time it is on the interfered frequency is so short you will never notice it.

Ken