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+15 votes

How many $8-bi$t characters can be transmitted per second over a $9600$ baud serial communication link using asynchronous mode of transmission with one start bit, eight data bits, two stop bits and one parity bit?

  1. $600$
  2. $800$
  3. $876$
  4. $1200$
asked in Computer Networks by Veteran (52.1k points)
edited by | 5.2k views

2 Answers

+32 votes
Best answer

The baud rate is the rate at which information is transferred in a communication channel.
Serial ports use two-level (binary) signaling, so the data rate in bits per second is equal to the symbol rate in bauds.

$\text{“9600 baud"}$ means that the serial port is capable of transferring a maximum of $\text{“9600 bits per second".}$

So, transmission rate here $=9600\text{ bps}$.

An eight bit data (which is a char) requires $1$ start bit, $2$ stop bits and $1$ parity bit $=12\text{ bits}$.

So, number of characters transmitted per second $=\dfrac{9600}{12}=800$.

Correct Answer: $B$

answered by Veteran (414k points)
edited by

@ arjun sir here bit rate is depend on what is encoding method ... is it ...?

in case of manchester encoding bit rate = 1/2 *baud rate 

or if NRZ encoding then bit rate = baud rate . .

so here nothing is mention about encoding how do you consider baud rate = bit rate ... by default it will be used or what is logic ..? 

or is it hit and try ...assume according to answer  

Nopes. This is fixed in "serial communication".
2 stop bits ????  Why stop bbits , plzzzzzz xplain the concept clearly,,,,
@Arjun sir, isn't this a synchronous transmission mode? I mean only asynchronous transmission mode requires start bit, stop bit, parity bit.

Synchronous transmission uses external clock to synchronous.

Accordingly, 9600/8= 1200. Here, 8 is the given 8-bits character.

So, option D

P.S. A similar question came in ISRO-2015 Set-A question number-51.
yeah you are right
–4 votes
baud rate  = 2* bit rate

bit rate = 9600 / 2 = 4800 bps

# of 8-bit character that can be send  =  4800 / (1 + 8 + 2 + 1) = 400 chars

as there is no option matching I will go with 800 chars.

option B
answered by Boss (13.4k points)
baud rate  = 2* bit rate

How is this?
Are these ques in syllabus ??
@Arjun, it seems like he is taking it as differential manchester/manchester encoding. There baud rate = 2 * bit rate. Though as no encoding is given, we got baud rate = bit rate here  !

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