Keep serial distribution simple with a passive splitter designed for one DCE device and four RJ45 connections. The Black Box TL421A is built for RS232 environments where the goal is to extend access, reduce cabling complexity, and preserve a direct, predictable signal path. Because it is passive, the TL421A avoids the power requirements and maintenance overhead of active serial distribution hardware. That makes it a practical choice for control rooms, equipment racks, and integration points where reliability and wiring discipline matter more than feature bloat. The four-port layout gives installers a clean way to fan out a single serial source to multiple endpoints while keeping the physical footprint and operational complexity low. For projects that still depend on RS232, this is the kind of accessory that earns its place by doing one job well: making serial connectivity easier to deploy and easier to maintain.