Standalone devices for retro computers are separate pieces of hardware connected to old computers (e.g., ZX Spectrum, Commodore 64) to expand their capabilities. Unlike cartridges that plug into a port, these are independent devices like external floppy drives, cassette emulators (e.g., Pi1541), joystick adapters, or printers (e.g., ZX Printer). They act as “add-ons” that make using retro hardware easier, such as speeding up game loading or connecting modern accessories. It’s like “retro tuning” for classic computer enthusiasts!