The different types of modern communication systems are:

Voice
Data
Video
Fax
Paging
Electronic mail

Let's take a few moments to discuss the different systems and the major components that make up the systems.

Voice

We are all familiar with our current telephone systems.  It is a very common device that many people take for granted.  The common telephone has a hand set that we speak into and listen on, a dial or key pad, and a cable or wire to connect it to the wall.  In home systems the wire normally leads to a central switch in a telephone building.  The switch controls the path that your telephone wires take as it connects you to the party that you called.  In some larger buildings or sites, like a school campus, a wiring closet may contain a switching unit also.  A switch is an electronic device that switches or channels all the phone connections to their proper destinations.  It's a simple device and very reliable. Radio is another form of voice communication and two-way radio is similar to telephone except that the transmission of the signal is wireless.  The voice signal can be transmitted by wire, fiber optic cable, or wireless means.

Data

Data communications can take many forms.  For the purposes of this class we will define data as that information that is stored and retrieved by computers.  Data flows through wires or fiber optic cables from one location to another.  Data does not really have components.  It is how information is stored.  It's most common form is the storage of information in a form that is represented by a series of zeros and one.   This is called binary data and when written or displayed it appears something like this "00110001".  The string of zeros and ones can be very long depending on the length of the computer word that it represents.  A series of eight bits or digits is called a "byte".  And normally two bytes make up a "word".  Sometimes the numbers are written in some other notation other than binary.  Two of these are octal which is a base 8 system and hexadecimal which is a base 16 system.  Using these systems saves a lot of space since it takes a lot less digits to represent a digital number.

Video

Video communications is a form of communication where the data being presented is in the form of moving images.  The components used with video are computers, cameras, projection screens, TV monitors, and cables.  The video data can be in digital format or analog.  The media used to transmit the signal is electromagnetic waves similar to those used by radio.

Facsimile

Facsimile or fax communication is the method used to transmit a paper document over telephone lines to some remote location.  In the most traditional sense of fax transmission a paper document is scanned for it's image content, transmitted over telephone lines to another fax, and the receiving machine converts the telephone analog signals back to digital signals and an image again.  The operation of fax machines is improving by using computers to originate or receive the document being transmitted.   Using a computer improves the image quality by eliminating the scanning process.   The components used for facsimile transmissions are telephone lines and sending and receiving fax machines.  Keep in mind that components used by telephones are also needed for facsimile communications.

Paging

Paging devices have improved tremendously in recent years.  Where they used to be one way devices giving only a telephone number as the message, they now can transmit detailed messages and two-way pagers can even reply to the message.  The newest pagers are closer to very small computers with cellular phone capability.  The component of paging devices is the unit itself.  It can be one-way only receiving messages only or two-way which allow communications both incoming and outgoing.

Electronic Mail

Electronic mail or e-mail is a relatively new form of communication.  Computers, and recently even pagers, are used to type messages that are then sent or transmitted to a mail server.  It is the function of the mail server to then send the message to the receiving computer.  The person receiving the message sees the written message on their computer screen.  They have the option of saving, deleting, or replying to the message.  One of the main advantages of e-mail over telephone conversations is that you can do e-mail at your convenience and the presence of the receiving party is not required.  The components used for electronic mail are personal computers, larger computers serving as mail servers, and some type of computer network.  In addition, software is required for posting mail and the server requires software that acts as a post office for the mail users.