Aug 02 2009
Telephony
Telephony has changed beyond recognition. Call waiting and conferencing are some examples of how our ordinary phones have changed.
Mobile telephones were almost unknown twenty years ago; now they are universal.
This picture shows the kind of mobile phone that would be found in a car. Not exactly an easy fit in your pocket, and a sizeable chunk out of your pay-packet.
You can see how the mobile telephone has decreased in size and weight from something approximating a brick, to a slim-line and natty little device that slips into your pocket (and out of it when you are not looking). Most of it is battery. There are many extra features in a mobile telephone:
- Different ring tones;
- Text messaging;
- Address book;
- Personal organiser;
- Web cam;
- Internet access.
Mobile telephones have their disadvantages:
- Unwelcome text message. When the “ambulance-chasing” law firm, Claims Direct went bankrupt, the owner dismissed all his staff by text message, owing them a lot of back pay. Some looted the offices for laptops instead of their pay. School bullies have been known to send unpleasant texts to their victims. Some companies are sending out “junk” text messages.
- The ringing tones can be very annoying.
- The telephones can ring in inappropriate places, for example a concert performance. A ringing mobile in an examination will result in instant and automatic disqualification.
- There are health concerns with the microwave radio waves used by the networks. These are thought to cause changes in the brain structure of young people. (Presumably in some older people there is not much brain structure to change.)
FAX
Facsimile machines (FAX) scan and digitise graphics and text. They transmit them as digital signals down telephone lines to another machine. Letters can be sent and received in minutes. However the quality is not as good as the original. Computers can send their output to a fax machine, which becomes, in effect, a remote printer.
Most fax machines can be used as a telephone. Some can also be used as
- a scanner,
- a printer,
- a photocopier.
Voice mail is the term given to those irritating machines that tell you to “Press 1 for account enquiries, press 2 for a new account, press 3 for a general inquiry.” They are more sophisticated answering machines, and many people use them in Call-back services. You can see how complex the navigation is around some voice mail systems. An internet site is easier to use.
Video-conferencing allows people in different locations to see and speak to each other. There are special cameras and microphones.
A computer with a device called a codec (coder-decoder) converts all the analogue sound and pictures into digital signals. They are transmitted over digital telephone lines called ISDN (Integrated Services Digital Network) which have the necessary bandwidth to allow the transmission of digital signals. PC users can work on the same document with similar, but simplified, equipment.
Advantages of videoconferencing are:
- Personnel remain available in the office.
- No need to travel, thus avoiding the stress caused by the traffic.
- No hotel bills, or paying for the hire of conference facilities.
- You can see the speaker, which you cannot with a telephone conference.
- Documents can be shared on stored onto other PCs.