This document discusses key concepts in signal transmission including: - There are two main types of signals - analog and digital. Analog signals are wave-based while digital signals are discrete zeros and ones. Conversion between analog and digital is sometimes needed. - Frequency refers to the number of complete cycles per second, with the unit Hertz. Amplitude is the magnitude of the wave at a given point. Bandwidth is the amount of data that can be carried in a given time period, usually expressed in bits per second. - Transmission can be synchronous, with data transferred in blocks, or asynchronous, transferring data character by character or frame by frame to accommodate slower or varying strength channels.

2. Signal
Presentation of value in terms of wave or discrete form is called
signal basically we have two types of signal. Analog are general
wave based signal. And digital signal are discrete (0&1)based
signal in data communication some time we have to convert the
signal from analog to digital and some time digital to analog

3. Frequency
The frequency of a periodic function is the number of
complete cycle that can occur per second. Frequency is
denoted with lower case ‘f’. Frequency has unite of Herz or
cycle per second.

4. Amplitude
The amplitude of the given wave is the value if the wave of
that point. Amplitude is also known as the magnitudes of
the wave at that point. There are no particular variable that
is used with amplitude, although capital A, capital M,
capital R are common

5. Bandwidth
The amount of data that can be carried from one point to
another in a given period of time (usually in second). This
kinds of bandwidth is usually expressed in bit of data per
second(bps).

6. Analog and digital transmission
There are tow types of transmission signal popular in the devices. Some devices
use digital signal directly and some need the conversion of signal to use. We
have to perform the digital signal due to following reasons.
1. Capacity utilization is high on digital signal.
2. It is easy to maintain privacy on digital processing.
3. It is the modern technology which uses discrete
signal to processing digital data.
4. It enhance the existing digital equipment.

7. Transmission impairments
Disturbance due to the communication media and
variation of signal and their frequency are called
impairments. There are three basic type of impairments .
They are given below.
Attenuation
Distortion
Noise

8. Attenuation
It is a phenomena where the strength of the signal is reduce and finally falls
off with some distances. We have to use some technique to reduce the
attenuation these are give below.
1. Increase the strength of the
signal and frequency to transfer
the signal .
2. Use the amplifier to or
repeaters to again and restore
it's original strength of the
signal

9. Distortion
Impairment due to the variation of the velocities of a signal is called
distortion. Due to this impairment the signal may varies so that recipient map
is not able to get the complete from of the signal such delay phenomena to
called delay distortion.
We can minimize such impairments
by selection the suitable
communication media specially the
wired transmission media.

10. Noise
Receptor will receive the signal with some unwanted signal
mixed with the original signal is called noise . Such noise are
mixed with the message signal form various sources these are
A. Thermal
B. Intermodulation
C. Cross talk
D. impulse

11. Synchronous and Asynchronous transmission
Synchronous
Transmission of data by making same
block and transfer in the form of
stream of block is called synchronous
transmission.
Asynchronous
Transmission of the signal with the
character by character or frame by
frame is called asynchronous
transmission it can transfer the signal
with low frequency speed channel
and the variation of the signal
strength of channels,