Explanation: GSM (Global System for Mobile Communications) allows multiple conversations to share one radio frequency channel through **Time Division Multiplex (TDM)**. With TDM, the available time on a single frequency is divided into very short, discrete time slots. Each user or conversation is assigned specific, recurring time slots to transmit and receive their digitized information. By rapidly switching between users' assigned slots, the system effectively interleaves multiple data streams on the same frequency, giving each user the impression of continuous access. **Frequency Division Multiplex (FDM)**, while also a method of sharing, works by assigning different, distinct frequency channels to each user. While GSM uses a combination of FDM (for allocating initial frequency bands) and TDM, TDM is the specific principle enabling multiple users *within* a single radio channel. **Double sideband** is a type of amplitude modulation (AM) technique, describing how information is impressed onto a carrier wave, not how multiple users share a channel.