INTRODUCTION TO TELEPHONE NETWORK
Define telephony and telephony system.
Define subscriber loop.
Explain the subscriber loop by drawing a simplified subscriber loop showing telephone set connected to a local exchange. Identify ‘tip’ and ‘ring’.
Explain the basic functions of a standard telephone telephone set. Draw a block diagram of a telephone set components : ringer circuit, on/off hook circuit, equalizer circuit, speaker, microphone, hybrid network and dialing circuit. Explain the function of each block. Explain the bandwidth of a voice channel in a telephone system.
Communication
Telecommunication
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The process of transmitting a message between two remote locations.
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- could be Voice, Music, Textual, Textual, Pictorial (graph, diagram, image, etc.) or moving image (video).
The telephone network, until the last decade, was almost entirely analog
The telecommunication telecommunication system is divided into four possible elements.
Telecommunication
End systems or instruments
Transmission
Switching
Signaling
There are 3 main parts as shown in above figure
Transmitting transducer
Receiving transducer
One pair wire system
Defination
T e l e p h o n y is the field of technology involving the
development, application, and deployment of telecommunication services for the purpose of electronic transmission of voice, fax, or data, between distant parties.
T e le le p h o n y s y s t e m - A system of telecommunications in which which
telephonic equipment is employed in the transmission of speech or other sound between points, with or without the use of wires.
The telephone network is made of 5 major components : End Instrument (Telephone) (Telephone)
Local Loop
Exchange
Trunk
Transmission Media
Figure : Major components components in telephone network
The telephone is a familiar end instrument in telecommunication telecommun ication switching system. The development development of telephon telephone e and circuits started around 1850. The table below shows the development of telephone.
The Main Distribution Frame is situated at the telephone exchange. It is used to connect the customer (phone user) with the main switching system after passing through the cabinet. It comprises of all the customers and data which are situated in one area or district.
To test the phone line.
To execute the jumper process.
To check the problem phone line.
To cut the phone line manually.
To connect the phone line manually
The cabinet Connection from the cabinet to the main distributor normally uses the ‘lead’ cable of different sizes where each of it has From the cabinet to the DP Box, it uses the plastic cable. In the cabinet, there From are
The Cabinet’s functions are as follo follows ws :
To save the usage of cable and replacing cable would be easier.
To avoid the joint to be opened and this would save cost and time.
To act as a place to perform maintenance checking.
To upgrade the arrangement of lines.
The DP Box’s function is . Usually, the DP Box from DP Box to the main distributor .
The upper cable is used . The two wire cable normally is used.
The underground cable is . The underground cable will end at the telephone exchange
TIP
RING
TIP is the ground side (positive)
RING is the battery (negative) side of phone circuit
TIP is The GREEN wire which is connected to the wall jack
RING is The RED wire which is connected to the wall jack
it used to provides the .
it function is to
Usually measures ground when on-hook
Usually measures -48Volts when on-hook
It requests the use of the telephone system when the handset is lifted. It indicates that the system is ready for use by receiving a tone, called dialing tone. It sends the number of the telephone to be called to the system. This number is initiated by the caller when the number is pressed or the dial is rotated. It indicates the state of the call in progress by receiving tones indicating the status (ringing, busy, etc).
It indicates an incoming call to the called telephone by ringing bells or other audible tones. It changes speech of the calling party to electrical signals for transmission to a distant party through the system. It change electrical signals received from a distant party to speech for the called party par ty.. It automatically adjust for changes in the power supplied it. It signals the system that a call is finished when a caller ‘hang -up’ the handset.
A telephone set is an apparatus that creates an exact likeness of sound waves with an electric current. The essential components of a telephone set are the
Human speech covers the frequency range of 100 to 7000 Hz (hertz) but research has shown that the intelligence intelligen ce part of human speech is carried in the 300 - 3400 Hz range. This range is called the Voice Band. The Voice Channel has a range of 0 to 4 kHz (4000 Hz). The area from 3400 to 4000 Hz is used for system control control and is called Out of Band Signalling.
Voice Channel 0-4,000 Hz
Voice Bandwidth 300-3,300 Hz
e g a t l o V
Guard Band
0
300
Guard Band
Frequency (Hertz)
3,300
4,000
Two Minute paper
