Many home automators have legacy systems linking to external control hardware via RS232. As times and (OS’s) have moved on many if us that ran multiple PCs have consolidated then into a single unit to ease management and running costs (as electricity prices have soared).
“The USB to Serial RS-232 Cable provides 2 or 4 (depending on model bought) RS-232 Serial (DB-9 male) connectors via one standard USB port. You can instantly enjoy connectivity with your Modem, PDA, POS or other serial devices on your PC or Mac without the hassle of opening your computer case. It provides a quick, simple and cost-effective solution and is ideal for various communication and automation applications.
Compatible with USB Specification v1.1 and v2.0 (Full-Speed) Supports 2/4 port Serial ports at the same time Supports all common RS-232 Serial Port Automatic USB Protocol handling Supports remote wake-up and power management USB bus powered, no external power supply required Requirements Available USB port Windows 2000, Windows XP, Windows Vista, Windows 7, & Mac.”