Monoprice 104640 RS232 Serial Mouse Monitor Splitter Cable

The Monoprice 104640 is a DB9 RS232 serial Y-cable designed for two specific legacy connectivity scenarios: splitting a 9-pin serial (RS232 COM) port to accommodate two serial devices, or providing dual 9-pin EGA/CGA video connections from a single source port. The cable's design is entirely passive — no active circuitry, no signal conditioning, no power requirement — which means its function is purely electrical: extending and splitting the pin connections of a DB9 serial interface. The RS232 standard is a decades-old serial communication specification still found on industrial equipment, vintage computers, CNC machinery, and certain specialized peripherals; the EGA/CGA video standard predates VGA and is specific to early IBM-compatible display systems from the mid-1980s.

This cable's practical audience is narrow but specific: technicians maintaining legacy industrial systems, retro computing enthusiasts running period-correct EGA/CGA display setups, and IT departments managing equipment with RS232 serial mice or terminals. For these scenarios, a quality passive Y-cable with lifetime warranty backing represents a reliable and cost-efficient solution compared to serial expansion cards or active USB-to-serial adapters. The critical limitation to understand before purchase is the VGA incompatibility — the DB9 physical form factor is deceptively similar to VGA's HD-15, but the two standards are entirely different at the electrical level, and this cable carries only RS232 data or 9-pin EGA/CGA video signals. Monoprice's rigorous quality control standards for cable products apply here, making this a dependable choice for a narrow but legitimate use case.