Introductory Communications
Modem and Digital & Analogue Data
Ordinary telephone lines can transmit sound signals because they are designed for speech. These signals are in analogue form. To transmit digital data into analogue data, it must be converted so when the analogue data reaches the end of the telephone line it must be converted back to digital format for a computer to accept it. A device called a MODEM (Modulator Demodulator) does this.
Differences
Analogue and digital data is very different. Digital lines are a lot more expensive to install and use compared to normal telephone lines. Modems must be purchased for use with normal telephone lines. Digital lines have a much higher bandwidth so the transmission rate for information is much quicker.
Advantages & Disadvantages
There are many advantages of using common networks, such as the internet, but there are also disadvantages. Local networks can mean that software and data can be shared, and all the users can communicate with one another. However, the installation software can be quite high and there is an extra task making sure that shared resources are safe and secure. The network can fail and cause chaos, or it could operate slowly if a lot of users are logged on.
User IDs and Passwords
When using a networked computer, it is important that we can only access data that is ours or that is shared. We shouldn’t be able to see other users’ personal data or documents. Each user then needs there own ‘logon’ identification and password. This is recognised by the system and the password attempts to ensure that the person is who they say they are. So it is important to keep the passwords private and change it frequently. They should ‘logoff’ the network properly.
Facsimile (Fax)
Fax machines are used to transmit documents which are not of personal nature. Immediate hard copies are printed at the other end, but the document cannot be sent if the fax machine is busy, and only one number can be used at one time. It is not possible to edit a fax or attach other files to it.
