Block Diagram of Communication System Video Lecture - NEET

hello friends this video on
communication systems part 4 is brought
to you by exam for your calm no move you
from exam so let us now try to
understand the block diagram of the
communication system so if somebody asks
you how does the communication system
work or can you explain me with the help
of a diagram how any in in general any
communication would work so in that case
you can just explain it with the help of
this diagram which looks very simple so
this is how the block diagram of a basic
communication looks like so here you
have the information source so this is
your information source from where the
entire information is going to come so
from the information source the
information comes in the form of message
signal right so we call this input
signal as the message signal so this
message signal comes to the transmitter
transmitter will convert it into a form
which is capable of being transmitted
and then it will send it so this is the
transmitted signal now this signal is
passed through a channel and then this
signal will be received by the receiver
so that is the received signal and then
the signal which is received by the
receiver
what will the receiver do the receiver
will take I mean convert the signal
again into a form which is
understandable by the user and then
again the message signal will get
converted into the user so you see here
the from what was the signal that came
out from the source it was a message
signal and what is the signal that is
delivered to the user that is again a
message signal so the same information
gets carried from one place to another
right so here you also see a new term
that is noise so noise also comes into
this channel now we will see what is
noise because these three transmitter
channel and receiver they are their
basic components which form the
communication system but other than that
also there are a couple of components
which also play a major or a very
important role in the communications
okay another small thing which I would
like you to note here is here I have
been using the word transmitter right
sometimes somewhere in your textbooks or
over the Internet
you might come across a term or
transducers and you might wonder that
transducers the purpose of a transducer
looks very similar to the purpose of a
transmitter and why do we have two
different terms okay let me talk about
transducer and transmitter for two
minutes so that you are clear with the
difference now basically why do we have
a transmitter here that is the first
question so that it can convert the type
of signal into a type of signal which is
capable of transmission for example if
it is a non electrical signal which is
coming from the source the transducer
will convert it into electrical signal
now you can tell me that is exactly what
a transmitter does because just now you
told that the job of transmitter is to
convert the signal into a form that is
capable of transmission and which form
of signal is capable of transmission
electrical signals so perfectly that is
what a transmitter does so why do we
have a transducer again so what's the
difference okay that's a good point or a
good question to be noted here now
transducers convert the mechanical
energy or any other form of energy into
electrical signals but the electrical
signals which are produced by
transducers are mainly in millivolts
right because whenever I talk of
electrical energy what am I talking
about basically I am either talking
about voltage or I am talking about
current because that is how we denote
electrical energy because we all have
studied and I'm sure I do not need to
explain you current voltage and all
those stuff again because we have
already gone through our lesson on
electronics like semiconductors we have
already studied all those stuff so we
are all aware of voltage current and
things like that so when I talk about
electrical signal so I am talking about
something like voltage or current
so these transducers what are they doing
they were actually converting the job of
transducer was to convert mechanical
energy or any other form of energy into
electrical signal but this electrical
signals was mainly in millivolts so
which is a very small voltage now
earlier there was no transmitter there
were only transducers and the purpose of
transducer was to convert non electrical
signals into electrical signals and
these electrical signals had I mean they
were they had lesser strength they were
in millivolts now it was them observed
that in order to transmit these
electrical signals over long distances
the signal strength should be higher if
the signals are just in millivolts when
it travels through the entire channel
sometimes it might be lost like I mean
it is something like this if a person is
strong we say that suppose if there is a
race where you have to run at a stretch
for 5 hours all you have to run at a
stretch for 10 kilometers so if the
person is strong enough we say that okay
he's a strong man so you can do it now
if the person is very weak and he's not
well he he is like not at all energetic
what do we see
oh no he'll not be able to travel fine
and he'll not be able to run for 10
kilometers right so that means if we
want the signal to travel for a large
distance we want the signal to be strong
enough but with the case of transducers
the kind of electrical signals which
they were producing they did not have
that much of strength so later with the
evolution of and improvement in
technology transducers output needed to
travel over long distances so there came
the limitation of transducers so
transmitters were developed to
compensate the signal loss due to
resistance and other interference now
the question is what happens in that
channel because of which the signals
strength might keep on decreasing we
will talk about that is where noise
please enroll we'll talk about that
later just leave that for the later
section but for now just understand that
if a person has to run for 10 kilometers
the person should have that much of
strength so that he doesn't fade away
somewhere in between so that is why try
on sweeter skin so what did the
transmitters do they converted the
millivolt signal output of transducers
into current for transmission so here
the transducers were producing voltages
in millivolts
now transmitters converted this
millivolts into current why did they
convert it into current that's because
if you make current to travel over a
distance they are less sensitive to
interference that means they are less
sensitive to resistances or noise or all
other kinds of interference so current
is a better option if you want you to
travel for longer distances because
current was less than sensitive so these
days what do people do these days we do
not have a separate transducer and a
transmitter so now you understand the
point this signal comes first it goes to
transducer which actually converts it
into an electrical signal of lesser
strength and then transmitter converts
those millivolts into current for better
transmission over long distances so
these days we do not have separate
transducers and transmitters these these
transducers are embedded with
transmitters so they both come together
so generally people call that as a
transmitter so anyway I say a
transmitter the transmitter definitely
has a transducer embedded in it right
so you understand your theory with the
concept of a transmitter and transducer
thank you
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