Data Transmission Modes.
The data Transmission modes or transmission of data over communication channels is made in three modes:
- Full duplex.
- Simplex Mode:
allows only one-way traffic. The devices using simplex mode of transmission, either send the data or receive the data; both functions are not possible.
- The half duplex mode:
allows two-way traffic, but one direction at a time. If the devices are sending the data it can not receive, it can not data. Wireless set uses the half-duplex transmission mode.
- Full – duplex Mode:
allows two traffic at a time. The devices using this mode of transmission can send and receive the data simultaneously. Telephonic communication is the example of full duplex mode.
Telecommunication processors are used to achieving the communication goals between the terminals and the computers in a telecommunication network. They perform a variety of functions in order to carry out the transmission of data Commonly used devices for telecommunication processing are:
- Front-end processors.
This communication processor is the most widely used device to connect computers over telephone lines. Ordinary telephone lines can carry only the analog signals. While the data inside the machine is in digital form So, to transmit this digital data over an analog channel, modems are used.
The speed of modem is measured in baud rate (explained earlier), it ranges from 9,600 bits per second to 56.6-kilo bits per second. These are available as:
- Internal direct connect modems are in the form of plug-in cards and connected inside the machine, the telephone line is connected to a jack.
- External direct connect modems are small stand-alone units, connected through a cable with the machine, the telephone line is connected to a jack.
Multiplexed allow sharing of the single communication channel by many terminals. Multiplexing is the process of merging the transmissions of several terminals into one stream and transmitting it over a single communication channel.
Concentrators concentrate many slow speed lines into a high-speed line through the use of buffer storage. They also route data to its proper destinations.
Private Automatic Branch Exchange.
This processor is also very common, found in almost every organization. It connects the trunk lines (telephone company’s lines) with the office telephone lines setup. They provide services like routing telephone calls, automatic call forwarding, conference calling, and dozens of other facilities.
Front End Processor.
When there are heavy data processing and data communication involved, the whole burden is not taken by a single machine. Generally, a small minicomputer is all ached with a mainframe to handle the data communication tasks and it is known as front end processor.