Definition

Serial interfaces work either in synchronous or asynchronous mode and are also known as synchronous or asynchronous serial interfaces.

The router supports RS-232, RS-422/RS-485, X.21, V.24, and V.35 physical serial interfaces.

• RS-232: an interface for exchanging serial binary data between two devices.
• RS-422/RS-485: an interface for exchanging serial binary data between devices. Compared to RS-232, RS-422 provides a faster transmission rate and longer transmission distance. (The maximum transmission rate decreases as cable length increases. The rate is about 10 Mbit/s at 12 meters, decreasing to about 90 kbit/s at 1200 meters.) RS-422 is a unidirectional balanced transmission standard that allows up to 10 receivers to connect to the balanced bus. RS-485 extends the interface applications of RS-422. It supports multi-point bidirectional communication, which allows multiple transmitters to connect to the same bus.
• X.21: An interface for exchanging signals between a data terminal equipment (DTE), such as a user computer, and digitalized data circuit-terminating equipment (DCE).
• V.24: An interface that supports both synchronous and asynchronous transmission modes. When working in asynchronous mode, a V.24 interface functions similarly to an RS-232 interface.
• V.35: is a general-purpose terminal interface standardized by the ITU-T for telephony network transmissions. This interface was originally a modem interface standard that uses bandwidths of numerous telephone circuits of 60-108 kHz base as a group to transmit synchronous data at 48 kbit/s. Currently, V.35 is mainly used on Nx64 kbit/s data interfaces and has been replaced by V.36 interfaces. However, V.36 interfaces are stilled called V.35 interfaces.

Purpose

The router uses the RS-232, RS-422/RS-485, X.21, V.24, and V.35 physical serial interfaces to implement leased line interconnections. Through these interfaces, the NE provides data access services at N x 64 kbit/s, or at sub-rates less than 64 bit/s, and transparently transmits the data over transmission or IP networks.

Benefits

Serial interface-based transparent transmission offers the following benefits to carriers:

• Lower network construction costs as dedicated lines for serial cables are no longer required
• Smooth network evolution, simplified network operating, and reduced maintenance costs