- 1. Lyell & Lee Transmitting & Recieving
- 2. Definition The information process that involves the transfer of data and information within and between information systems
- 3. Introduction Transmitting and receiving is the transfer of data within and in between information systems. Data is transferred between computers and devices in two ways: Serial Transmission and Parallel Transmission. Parallel Transmission is the transmission of pieces of data simultaneously using separate lines. Serial transmission is the transmission of pieces of data one after the other. Serial transmission is used in many devices such as mice, keyboards, modems and plotters. Parallel is used for most printers. For data and information to be exchanged between information systems, compatible communication systems are required. This is referred to as hand-shaking. Communication settings include baud rate, parity and file transfer protocol. The internet is a tool used by millions of people to transmit and receive information.
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- 6. Communication Concepts Asynchronous Transmission: Serial Transfer that sends one byte at a time with special start and stop bits. This has become the standard for personal computers. A parity bit is used to check for errors in transmission. Synchronous Transmission: Serial Transfer were data is sent at the same rate. It is faster and more efficient then a Asynchronous Transmission, and is used on larger computer systems. Simplex mode: The transmission of data in one direction only, from the centre to the receiver. It is Limited and not widely used in telecommunications.
- 7. Communication Concepts Pt.2 Half Duplex mode: The transmission of data in both directions but not at the same time. This means the sender and receiver takes turns. Full Duplex mode: The transmission of data in both directions at the same time. Buad Rate: A measure of the maximum number of data symbols or electrical that can be sent per second over the communication link. Bits per second: A unit of measurement for the speed of data transfer. It can be different to the board rate because a data symbol may contain more then one bit of data. For example, a 240bps device might operate at 600 baud.
- 8. Role of Modem
- 9. The role of the Modem A modem is a device that enable data to be transmitted from one computer to another. The word Modem stands for Mo dulator/ dem odulator. A modem converts digital signals sent from a computer into analog signals suitable for transmission on a telephone line. Analog signals are pulses in the form of waves. When the signal is received by another modem, it reverses the process by converting the analog signal into a digital signal. Depending on the medium used, they can be electrical pules or light pules. A direct connect modem is the most common type of modem as it is connected directly to a telephone line. Most modems use a command set developed by hayes and are described as “Hayes compatible”.
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- 12. Communication software It uses protocols to establish a connection. A protocol is a set of rules that governs the transfer of data between hardware. It defines how the information is transmitted and how errors are detected. The 2 pieces of hardware must use the same protocols, otherwise the data transfer may be unsuccessful. Some popular protocols for networks are Ethernet and token ring. This image shows how important communication software is because it allows and manages the transfer of data, files and commands between different types of hardware.
- 13. Data Encryption This image represents data locked inside the computer. This is used to stop data being intercepted and read during transmission. Data is scrambled so that it is meaningless to anyone other than the recipient, who uses the same encryption software to convert it back. A popular encryption method is Secure Socket Layer (SSL)
- 14. Email Electronic mail allows communication with other users by sending and receiving electronic messages using a computer. Email messages are often short and are typed quickly. Messages are written offline and sent when the user logs onto the LAN or Internet. Attachments are computer files sent with email messages, such as image, audio, video or text files.
