It is contained within walls of the area and it's the only system appropriate for confidential transmission. Receivers must be within line of sight of the transmitter. AM Systems - AM systems are similar to FM systems. Receivers, which may be AM radios in some cases, pick up the signal broadcasted from an AM radio transmitter coupled to a microphone or PA system. The technology is both simple and inexpensive.
Users have the freedom to choose where they want to sit.
Users can bring their own personal AM radio and attachments and fine-tune to the broadcast. They are rarely used now and suppliers may be hard to find. For assembly areas without amplification systems and for spaces used primarily as meeting and conference rooms, a permanently installed or portable system shall be provided. If portable systems are used for conference or meeting rooms, the system may serve more than one room. If the listening system provided serves individual fixed seats, then such seats shall be located within 50 ft.