The 803 master station is a rack-mountable unit (2U height) that serves as the core of a professional intercom system. It includes a built-in speaker, front panel headset connections, a panel microphone input, and a 16-button keypad for operation and programming. Designed to be highly flexible, it features user-programmable settings that allow customization of communication tasks. The circuitry for optional four-wire operation, IFB (Interruptible Foldback) panel emulation, and ISO (Isolation) panel emulation is integrated, requiring only an optional connector cable and internal DIP switch settings to activate these features.