If you had a handful of transmitters, all on the same frequency, transmitting at various intervals, it would be useful for distinct transmitters to use different subcarrier frequencies or something, to allow the receiver to determine which is which.
If you had a handful of transmitters, all on the same frequency, transmitting at various intervals, it would be useful for distinct transmitters to use different subcarrier frequencies or something, to allow the receiver to determine which is which.