RS-232 defines the meaning of the different serial signals and their respective pin assignments on a standard 25-pin (DB-25) serial connector.Table 1 (a plain text version is also available) shows these assignments.
RS-232 defines the meaning of the different serial signals and their respective pin assignments on a standard 25-pin (DB-25) serial connector.
In this case, serial cables simply leave the unused pins disconnected.
There are two cable configurations in use today for serial equipment: These different configurations determine which signal a device expects on which pin. Because terminals are typically DTE, and modems are typically DCE, you must use a different cable between a computer and a terminal than between a computer and a modem.
DIN-8 serial connectors are small, and almost circular.
They are used on Macs, and often on laptops because they are so compact.
This is something to keep in mind when connecting terminals to computers in other rooms.
Because of the fact that RS-232 defines signals that go unused in standard types of communication, and because the traditional DB-25 connector is large an unwieldy (especially for small equipment, like laptops), many alternate serial connectors have come into widespread use.For instance, with a terminal, it lets you use only 3 wires for a connection: transmitted data, received data, and signal ground.However, in a modem connection, you really want to pay attention to DCD.In fact, it's overkill for most standard communication.However, it's good enough to have become an industry standard.This is a pretty conservative figure and has been stretched as far as 1,000 feet.How far the limit can be stretched depends on the brand of terminal and computer you are using.RJ-45 connectors look a lot like standard telephone connectors ... They house eight wires instead of the four wires in a telephone connector.RJ-45s are not typically found on computers or normal serial equipment, but, because they are so small, they are often used on devices that have a lot of ports very close together.We will talk more about this cabling difference later.The RS-232 specification defines the the maximum length of serial cable to be 75 feet at 9,600 bps.