A transmission uses EBCDIC. The 48.8 Kbps transmission scheme has a
390 character block with 12 control characters per block. This
half-duplex circuit has a reliability of 99.5% and a turn-around delay
of 3 msec. What is its TRIB? Answers are approximate.

 40 Kbps 
 43 Kbps 
 45 Kbps 
 47 Kbps 
 none of the above 
 Don't know. Not enough information provided.

Hi valbuenahector!!

·Character (Char) Information:
K = information bits + control bits = 8 bits/char + 1 bit/char = 9 bits/char 


·Block Information:
M = total characters = 390 char/block 
C = control characters = 12 char/block 
I = information characters = (M-C) = 378 char/block 
P = % of errors = 1 - 0.995 = 0.005 = 0.5%


·Time
T = turnaround time = 0.003 sec 
R = transmission rate = 48,800 bits/second = 5422.22 char/sec

Note: M is in characters while R is in bits/sec. In order for the
units to "cancel out" in calculations their units must be
"compatible".


The transmission rate of information bits (TRIB) formula is:

         K*I*(1-P)        9*378*0.995          
TRIB = ------------ = -------------------- = 45177.62 bits/sec
        (M/R) + T     (390/5422.22)+0.003     
   

TRIB = 45 Kbps aprox.


I hope that this helps you. feel free to request for a clarification
if you need it.

Best regards.
livioflores-ga

great answer