Serial-data transmission where bits are continuously transmitted in a single transmission line. Most common serial data transmission method is called RS-232 (Recommended Standard 232). RS-232 specifies Physical layer values like voltage, timing, and compatibility. This standard is used with most common connectors – RJ-45, DB-9, and DB-25, or lotus screw type, as used in our video over fiber equipment series.
Serial cables are mostly used by the administrator for connecting external modem/router to the workstation for its configuration and management. High end networking equipment is being shipped with RS-232 compatible serial cable. Although, administrator could access network equipment remotely, sometimes network might be malfunctioning, and requiring direct management of some device.
Figure 1. RS-232 supporting connectors.
Serial cables might have different connectors, but have the same purpose. Such as Cisco routers are being shipped with RJ-45 console port. The same way as twisted pair cable, serial cable termination points can vary in arrangement depending on its purpose. Pins can be reversed in order to create crossover cable. Crossover serial cable can be used for connecting two routers through serial ports.
