1. The normal ringing signal amplitude and frequency are:
(i)
60 V rms at 30 Hz
(ii)
90 V rms at 20 Hz
(iii)
90 V rms at 30 Hz
(iv)
60 V rms at 20 Hz
(v)
30 V rms at 20 hz
2. A computer puts its RTS line “HIGH”.
a)
How much voltage that will be on RS-232 side-------------------------.
b)
Does it represent “ON” or “OFF” condition----------------------------.
c)
Is it called “MARK” or “SPACE”-----------------------------------------.
d)
What is the name of the equivalent signal generated by the modem.---------------------------.
3. A signal is to be transmitted at 29.6Kbps through a noisy channel whose signal to
Noise ratio is 20 dB (Power). Calculate the BW required. Can this signal be
transmitted over the Public Switched Telephone Line?
4. For the circuit shown, calculate the output voltage Vo and the input and output
power in dBm. Show your work. Use back of the page.
Gain 10dB
Vo
S.G
Cable loss = 6dB
Vi= 3V
GND
600 Ohms
600 Ohms
GND
GND
5. An analog signal of 5 KHz is being sampled at 9 KHz. Sketch the frequency
spectrum of the S/H circuit upto 30 KHZ
V
Hyder Khoja
Page 1
3/8/2016
F
6. A PCM/TDM system multiplexes 30 voice band channels. Each sample is
encoded into 7 bits and one extra bit is added to each frame as a frame
synchronization bit. The sampling rate is 8kHz.
a) What is the time of one frame:-------------------------------------------------b) What is the time of one bit:------------------------------------------------------c) What is the bit transmission rate:-----------------------------------------------7. For the Data bits shown, sketch
(i)
The B8ZS-AMI waveform
(ii)
The Manchester coded waveform
1
(b)
0 1 11 0 0 0 0 0 0 0 0 0 1 0 0 1
Specify two reasons for line encoding:
________________________
©
__________________________
In the N. American PCM/TDM System, where is the Signaling Information
stored : _______________________________________________________________
8.
Consider the 12 bit code generated by an A/D converter
100111101011
(a)
Showing each step, generate the 8 bit compressed code.
(b)
Reconstruct the 12 bit code from (a) above
Hyder Khoja
Page 2
3/8/2016
9. Given the 8 bit data sequence 1 0 1 0 0 1 1 1 and a G(X) = 1 0 1 1. Find:
a)
The M(x): (1)
b)
The Remainder: (2)
c)
The T(x): (1)
d)
Draw a circuit to implement the given divisor (2)
10
Show connections to perform the Local LOOPBACK test of the CODEC IC
shown below (5)
TXD
RXD
1
4
L
C
5
4
8
0
FST/R
BIT CLK
+5V
Hyder Khoja
Page 3
AUDIO IN
AUDIO OUT
GRN
3/8/2016