The difference is that voice traffic is digitized, compressed, and multiplexed to save space. Two slots make up one voice circuit. By the number of samples taken, when speech is first converted to digital. If not, go back . Let's look at what's contained in just one slot of half a frame in digital cellular.
All numbers refer to the amount of bits.
Note that data fields and channels change depending on direction. Keeps one time slot or data burst separate from the others. Lets the transmitter go from a quiet state to full power. The data bits of the actual conversation. Digital verification color code.