Which type of signal is used to produce a predetermined alteration in the carrier for spread spectrum communication?

In spread spectrum communications, the transmitter uses a specific code to dictate how the signal is spread (in direct sequence) or hopped (in frequency hopping). This code is generated using a pseudo-random sequence. It appears completely random to outside interference, giving the signal its noise immunity, but it is mathematically predetermined. Because the sequence is predetermined, the intended receiver can generate the exact same pattern to synchronize with the transmitter and decode the data. A truly 'random noise sequence' would make it impossible for the receiver to ever decode the transmission.