The document discusses basic low voltage systems including telephone, internet, and intercom systems. It provides definitions and histories of internet and describes basic internet services like email, file transfer protocol, and telnet. It discusses the evolution of the telephone from its invention by Graham Bell to modern smartphones. It also explains how cellular networks work using base stations and switching centers to handoff calls between cells as users move. Finally, it defines basic components and terms for intercom systems, including master stations, door stations, and various intercom connection devices.

1. BASIC LOW VOLTAGE SYSTEMS
CHAPTER 15.2
TELEPHONE,INTERNET&INTERCOM
By
Dinesh Kumar Sarda

2. INTERNET
INTERNET

3. CONTENTS
 Definition And History
 Basic services of INTERNET
 The World Wide Web (W.W.W.)
 WWW browsers
 INTERNET search engines
 Uses of INTERNET

4. Definition and History
 The INTERNET is a network of computers,
which links many different types of computers
all over the world.
ARPANET was the first WAN and had only four
sites in 1969.
In 1989, the U.S. government lifted
restrictions on the use of INTERNET, and allow
its usage for commercial purposes as well.

5. BASIC SERVICES OF INTERNET
Electronic Mail (E-Mail)
File Transfer Protocol (FTP)
Telnet

6. Electronic Mail (E-Mail)
Allow user to send a mail (message ) to
another internet user in any part of the world
in a near-real-time manner.

7. E-Mail is a rapid and productive communication tool because :
 It is faster than Paper Mail.
 Unlike telephone, The persons communicating
with each other need not to be available at
the same time.
 Unlike Fax documents , Email documents can
be stored in a computer and be easily edited
using editing programs.

8. FILE TRANSFER PROTOCOL
Allow user to move a file from one computer
to another on the internet.

9. FTP
 Moving a file from a remote computer to ones
own computer is known as Downloading.
 Moving a file from ones own computer to a
remote computer is known as Uploading.
 Anonymous FTP site in a computer allows a user
to log in with the username of anonymous and
password that is user’s E-mail Address.
 Anonymous FTP sites are called publically
accessible sites because they can be accessed by
any user on internet.

10. TELNET
• Allow a user to log into another computer
somewhere on the internet .

11. Some common uses of telnet service are :
 Using the computing power of the remote
computer.
 Using a software on the remote computer.
 Accessing remote computers data base or
achieve.
 Logging into ones own computer from another
computer.

12. WEB BROWSERS
To use a computer as a Web client, a user
needs to load on it a special software tool
known as WEB Browser.

13. Browser provide following navigation facilities
 Do not require a user to login to a server computer.
 Enable a user to visit a server computer’s site directly and access
information on it by specifying its URL (Uniform Resource Locator).
 Enable user to create and maintain a personal hotlist of favorite
URL.
 Maintain a history of server computers visited by user in a surfing
session.
 Enable a user to download information in various formats.

14. INTERNET SEARCH ENGINES
Internet search engine is an application, which helps users to
locate Web sites containing useful information and
references.
To search Information :
 A user types the description of the information using the
user interference of the search engine.
 The search engine then searches the requested information
on the WWW and returns the results to the user.
 Results enable the user to locate the requested quickly
from the last ocean of information available on the internet

15. Some Popular Internet Search Engines

16. SOME COMMON USES OF INTERNET
On-line communication.
 Software sharing.
 Exchange of views on topics of common interest.
 Posting of information of general interest.
 Organization promotion.
 Product promotion and feedback about products.
 Customer support service.
 On-line journals, magazines, Encyclopedia.
 On-line shopping.
 World-wide conferencing.

17. The Evolutionof the Telephone
INVENTED BY GRAHAM BELL

18. TELEPHONE
The Telephone was patented on March 7th , 1876
The first telephone call was made on March 10th ,
1876.
The first words ever heard on a telephone: “Mr.
Watson--come here--I want to see you”
These words were exchanged between Alexander
Graham Bell and Thomas Watson.
The first transcontinental call was made between
San Francisco and New York

19. Hand Cranked Wall-1880’s

20. Candlestick-1890’s

21. Cradle Phone-1890’s

22. Candlestick Rotary-1914

23. Desktop Rotary-1920’s

24. Touchtone-1960’s

25. Wall Touchtone-1970’s

26. Mobile/Cellular-1983

27. Candy Bar-1990’s

28. Clamshell/Flip

29. Sliding/Qwerty Keyboard

30. Smart Phone

31. Touch Screen

32. iPhone

33. VoIP: Voice over (eg, Skype, Vonage)

34. Cell phone works on Electromagnetic Waves

35. What is a Cellular Network ?
 A cellular network or mobile network is a
wireless network distributed over land areas called
cells, each served by at least one fixed-location
transceiver, known as a cell site or base station.
A cellular network is a radio network made up of a
number of radio cells (or just cells) each served by at
least one fixed-location transceiver known as a cell
site or base station.

36. Working of CELLULAR NETWORK
MSMobile station; BSTBase station transceiver; MSCMobile
switching center; BSCBase station controller;
PSTNPublic switched telephone network

37. The area (a city, or a part of town) is divided into a
number of cells (typically 2 to 10 miles in size, but can be
smaller for more crowded areas) and a base station is
positioned within each cell.
If a user (mobile phone) is within a particular cell, the call
is handled by the corresponding base station within that
cell
The base station transmits the signal to the mobile
switching center (MTSO) which switches the signal to
another base station, or to a Public Switched Telephone
Network (PSTN), depending on the destination of the call:
whether another mobile unit or a regular telephone
As a user moves from one cell to another, the call is
“handed over” to the base station of the other cell-This is
called hand-off

38. The Mobile phone network
The most common example of a cellular
network is a mobile phone (cell phone)
network.
A mobile phone is a portable
telephone which receives or makes calls
through a cell site (base station), or
transmitting tower.
Radio waves are used to transfer signals to
and from the cell phone.

39. Advantages Of Cellular Systems
Mobile network providers install several thousands of base stations
each with a smaller cell instead of using power full transmitters with
large cells because, when the cell size is small we can have the
following advantages:
1. Higher capacity
2. Less transmission power
3. Local interference only
4. Robustness

40. Disadvantages Of Cellular Systems
Some of the disadvantages of cellular systems are:
1. Infrastructure needed
2. Handover needed
3. Frequency planning

41. INTERCOM
An intercom (intercommunication
device), talkback or door phone is a stand-
alone voice communications system for use
within a building or small collection of
buildings, functioning independently of
the public telephone network

42. Basic intercom system terms
• Master Station or Base Station – These are units that can control the system, i.e.,
initiate a call with any of the stations and make announcements over the whole
system.
• Sub-station – Units that are capable of only initiating a call with a Master Station
but not capable of initiating calls with any other stations (sometimes called slave
units).
• Door Station – Like sub-stations, these units are only capable of initiating a call to
a Master Station. They are typically weather-proof.
• Intercom Station – Full-featured remote unit that is capable of initiating and
receiving party-line conversation, individual conversation and signaling. May be
rack-mounted, wall-mounted or portable.
• Wall Mount Station – fixed-position intercom station with built-in loudspeaker.
May have flush-mounted microphone, hand-held push to talk microphone or
telephone-style handset.

43. • Belt Pack – portable intercom station worn on the belt such as
an interruptible feedback (IFB) with an earpiece worn by talent.
• Handset – permanent or portable telephone-style connection to an
intercom station. Holds both an earpiece and a push to talk
microphone.
• Headset – portable intercom connection from a belt pack to one or
both ears via headphones with integrated microphone on a boom
arm. Connects to a belt pack.
• Paging Signal – An audible and/or visual alert at an intercom
station, indicating that someone at another station wants to initiate
a conversation.
• Power Supply – Used to feed power to all units. Often incorporated
into the design of the base station.