Differences in Telecommunication Terms

This paper will attempt to define and contrast the following terms:

a. Synchronous and asynchronous

b. Analog and digital

c. XON and XOFF

d. Simplex and duplex

e. Serial and parallel transmission

f. Baseband and broadband

g. Serial Line Internet Protocol (SLIP) and Point-to-Point Protocol (PPP)

h. Hypertext Transfer Protocol (HTTP) and File Transfer Protocol (FTP)

i. Transmission Control Protocol (TCP) and Internet Protocol (IP)

It will also contain a brief description and analysis of the OSI layers that are used with the TCP/IP protocol stack.

Synchronous and Asynchronous

In referring to the signal that passes through telephone lines, the transfer methods may be either synchronous or asynchronous. A synchronous data transfer is sent in a continuous, single stream of characters, grouped into buffered bits. Before the transmission is sent, synchronous characters are sent that set the sending and the receiving ends to the same time. Once affirmation of the syn pulse is returned, the stream is sent to the receiving end.

An asynchronous data transfer consists of start and stop bits at the beginning and the end of the pulses that are sent. (Modem, 2004)

Analog and digital

An analog signal is an exact replica of the sound or picture being transmitted. An analog wave signal is a signal that consists of changing amplitudes of frequencies. An analog transmission is used over telephone lines to transmit voice frequencies over a carrier frequency through the telephone line. An electric current reproduces the frequency for transmission, then it is converted at the other end back into the sound wave.

A digital signal is a square wave signal consisting of a voltage and then a lack of voltage. Digital transmission involves laser lights that flash on and off and are carried through fiber optic lines. This is a very fast transmission rate (approximately 450 flashes per second) and can result in two fiber optic transmission lines to be able to transmit almost 15,000 conversations at the same time. Digital transmission is faster than analog, and also is more stable, as less noise or other interference can disrupt the signal. (Thinkquest, 2004)

XON and XOFF

Control characters like XON and XOFF are used to set limits on the transmission of data. Control characters are used when sending data to a printer, monitor, modem, or other device. XOFF (usually referenced by CTRL+S) is used by the transmitting side at the end of the data pulsed to say that the transmission batch is complete. XON (usually referenced by CTRL+Q) is used to start the transmission, and is found at the beginning of the data pulse. (ComputerHope, 2004)

Simplex and duplex

A simplex data transmission is only sent one way and without control characters or error signals. An example of a simplex transmission would be the alarm codes that are sent to officials at a burglar alarm company.

A half- duplex transmission can send a signal and then receive a signal, but cannot send and receive at the same time. An example would be a CB radio that can send a message, and then listen for the response.

A duplex data transmission is capable of sending and receiving data at the same time. A telephone line is an example of a full duplex transmission system. (Eserver, 2004)

Serial and parallel transmission

Serial transmission is the consecutive transmission of the signal. The characters are transmitted in a sequence over a single line, rather than simultaneously over two or more lines, as in parallel transmission.

Parallel transmission are packets of data sent at the same time, usually over more than one transmission line. This results in faster transmission of data. Many times, this data is sent sporadically, and start and stop characters are used, along with other control characters to ensure that the receiving end can put the packets back together in the correct order. (Freedictionary, 2004)

Baseband and broadband

Very simply put, baseband transmission is a form of serial transmission in that it transmits only one signal at a time. Broadband transmission is a form of parallel transmission, in that it can transmit multiple signals simultaneously. (Ckslsc,