Data transmission mode

Most internal PC data channels support simultaneous bi-directional flow of signals, but communication channels between the PC and the outside world are not so robust.

Here you will be learning about the different alternatives that are available for the design of communication channel. These alternatives apply to both Analog and Digital channels and they are:
* Simplex
* Half duplex
* Full duplex Simplex

The simplest signal flow technique is the Simplex configuration. Simplex allows transmission in only one direction and is a unidirectional channel. Note the difference between simplex and half-duplex.

Half-duplex refers to two-way communications where only one party can transmit at a time.

Simplex refers to one-way communications where one party is the transmitter and the other is the receiver. An example of simplex communications is a simple radio or television, which you can receive data from stations but can't transmit data.

Advantages of Simplex
* Cheapest Communication method

Disadvantages of Simplex
* Only allows for communication in one direction

Half Duplex
Half Duplex refers to the transmission of data in just one direction at a time. For example, a walkie-talkie is a half-duplex device because only one party can talk at a time.

In contrast, a telephone is a full-duplex device because both parties can talk simultaneously.Most modems contain a switch that lets you select between half-duplex and full-duplex modes. The correct choice depends on which program you are using to transmit data through the modem.

In half-duplex mode, each character transmitted is immediately displayed on your screen. (For this reason, it is sometimes called local echo -- characters are echoed by the local device).

In full-duplex mode, transmitted data is not displayed on your monitor until it has been received and returned (remotely echoed) by the other device. If you are running a communications program and every character appears twice, it probably means that your modem is in half-duplex mode when it should be in full-duplex mode, and every character is being both locally and remotely echoed.

Advantages of Half Duplex
* Costs less than full duplex
* Enables for two-way Communications.

Disadvantages of Half Duplex
* Only one device can transmit at a time
* Costs more than simplexFull DuplexFull Duplex refers to the transmission of data in two directions simultaneously.

For example, a telephone is a full-duplex device because both parties can talk at once. In contrast, a walkie-talkie is a half-duplex device because only one party can transmit at a time.

Most modems have a switch that lets you choose between full-duplex and half-duplex modes. The choice depends on which communications program you are running.In full-duplex mode, data you transmit does not appear on your screen until it has been received and sent back by the other party. This enables you to validate that the data has been accurately transmitted. If your display screen shows two of each character, it probably means that your modem is set to half-duplex mode when it should be in full-duplex mode.

Advantages of Full Duplex
Enables for two-way Communications simultaneously.

Disadvantages of Full Duplex
The most expensive method in terms of equipment because two bandwidth channels are needed.