RS 449

In this article we will discuss RS 449, will make brief discussion on RS 449, In last article we discuss about Optical Transport Network.

The RS-449 specification, also known as EIA-449 or TIA-449, defines the functional and mechanical characteristics of the interface between data terminal equipment, typically a computer, and data communications equipment, typically a modem or terminal server.

RS449 is a specification for a differential communications interface that uses a DB-37 connector and differential equivalents of the V.24 (RS-232) signals. Alternatively referred to as the EIA/TIA-449, the RS-449 is short for Recommended Standard-449. It is a data standard that specifies the functional and mechanical characteristics of the interconnection between DTE and complying EIA electronic standards RS-422 and RS-423. The RS-449 standard is commonly found in data network communication equipment. Below is a layout of the 37-pin configuration for the RS-449, starting with pin 1 that is located at the top left of the connector.

RS449 interface

One of the ways in which the RS449 data communications standard is able to send at high speeds without stray noise causing interference is to use a differential form of signalling. Earlier data communications standards such as RS232 used signalling that was referenced to earth and while this was easier to implement and cheaper to cable, it introduced limitations into the system.

By using twisted wire pairs for the data lines, any unwanted noise will be picked up by both wires together. As the RS449 receivers use a differential input, and they are not referenced to ground, any noise that is picked up does not affect the input. This means that higher levels of noise can be tolerated without any degradation to the performance to the data communications system.

In order to minimise any confusion that could easily occur, the circuit abbreviations have been changed. In addition to this the RS449 interface requires the use of 37 way D-type connectors and 9 way D-type connectors, the latter being necessary when use is made of the secondary channel interchange circuits.

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