We are not talking about your breakfast cereal today. No! We are talking about serial technology. Serial communication has been used by computers for many years, though not as widely used in today’s market. When most people refer to serial, they think of the DB9 cable. It is referred to as DB9 because it carries 9 pins within it. DB9 was typically used for devices such as gamepads, mice, keyboards, or other such interface devices.
What we have here is a FireFold brand 6 foot DB9 female to female serial null modem cable. Null modems are usually used to connect DTE (data terminal equipment) like terminals or printers together using a RS-232 cable. Originally, the RS-232 standard was developed and used for teleprinter machines which could communicate with each other over phone lines. This was so that you would not have to use an actual modem for transferring of information between the two devices.