A multimeter is an electronic instrument that can measure voltage, current, and resistance. It uses a galvanometer connected in different circuit configurations to perform these measurements. As a voltmeter, a high resistance is connected in series with the galvanometer. As an ammeter, a low resistance is connected in parallel. To measure resistance as an ohmmeter, a battery and variable resistor are used in the circuit. Multimeters are widely used for testing and troubleshooting electronic circuits.

1. SILICON CONTROLLED RECTIFIERS
The silicon controlled rectifier is a three terminal semi conductor
switching device which is probably the most important cct element
after the diode & the transistor.
The SCR has appeared in the market under different names such as
thyristor, thyrode and transistor.
A Silicon Controlled Rectifier is a semiconductor device that acts as a
true electronic switch. It can change alternating current into direct
current.
P N P N

2. TRANSFORMER : -
ITS JOB IS EITHER TO STEP UP OR MOSTLY STEP DOWN THE A.C. SUPPLY
VOLTAGE TO SUIT THE RECUIREMENT OF THE SOLID- STATE
ELECTRONIC DEVICES AND CIRCUITS FED BY THE D.C. POWER SUPLY. IT
ALSO PROVIDES ISOLATION FROM THE SUPPLY LINE-AN IMPORTANT
SAFETY CONSIDERATION.
Schematic symbol of transformer
Black or white Red
RS= 40n
SECONDRY RP= 40n PRIMARY
Green Blue

3. TYPES OF TRANSFORMER
1. STEP UP TRANSFORMER.
2. STEP DOWN TRANSFORMER.
Voltage Ratio of transformer = VP = NP
S V
S N
STEPDOWN TRANSFORMER
Blue Green
PRIMARY SECONDRY
Red Black or white
STEP UP TRANSFORMER
Blue Green
PRIMARY SECONDRY
Red Black or white

4. INTRODUCTION
In recent years, the rapid strides and remarkable
advances in the field of electronics is parrtly due to
modern electronic instruments. By using these
instruments, we can gather much information
regarding the performance of specific electronic cct.
Electronic Instruments.
Those instruments which employ electronic
devices for measuring various electrical quantities (e.g
voltage current, resistance etc.) are known as
electronic instruments.

5. MULTIMETER
• MULTIMETER IS AN ELECTRONIC INST WHICH CAN
MEASURE RESISTANCE, CURRENTS AND VOLTAGES. IT IS
AN INDISPENSABLE INST AND CAN BE USED FOR
MEASURING DC AS WELL AS AC VOLTAGES AND CURRENTS.
MULTIMETER IS THE MOST INEXPENSIVE EQUIPMENT AND
CAN MAKE VARIOUS ELECTRICAL MEASUREMENTS WITH
REASONABLE ACCURACY.

6. FUNCTION OF MULTIMETER
• A MULTIMETER CAN MEASURE VOLTAGES, CURRENTS
AND RESISTANCE. TO ACHIEVE THIS OBJECTIVE,
PROPER CIRCUITS ARE INCORPORATED WITH THE
GALVANOMETER. THE GALVANOMETER IN A
MULTIMETER IS ALWAYS OF LEFT ZERO TYPE i.e.
NORMALLY ITS NEEDLE RESTS IN EXTREME LEFT
POSITION AS COMPARED TO CENTRE ZERO POSITION
OF ORDINARY GALVANOMETERS.

7. MULTIMETER AS VOLTMETER
• WHEN A HIGH RESISTANCE IS CONNECTED IN
SERIES WITH A GALVANOMETER, IT BECOMES
A VOLTMETER.

8. MULTIMETER AS AMMETER
• WHEN LOW RESISTANCE IS CONNECTED IN
PARALLEL WITH A GALVANOMETER, IT
BECOMES AN AMMETER.

9. MULTIMETER AS OHMMETER
• AS PER THE FIG THE MULTIMETER EMPLOYS THE INTERNAL
BATTERY. A FIXED RESISTANCE R AND A VARIABLE RESISTANCE R
ARE CONNECTED IN SERIES WITH THE BATTERY AND
GALVANOMETER. THE FIXED RESISTANCE R LIMITS THE CURRENT
WITHIN THE RANGE DESIRED AND VARIABLE RESISTANCE R IS FOR
ZERO ADJUSTMENT READING. THE RESISTANCE TO BE MEASURED IS
CONNECTED BETWEEN TERMINALS A AND B. THE CURRENT FLOW
THROUGH THE CIRCUIT WILL DEPEND UPON THE VALUE OF RESISTOR
CONNECTED ACROSS THE TERMINALS. THE OHMMETER SCALE IS
CALIBRATED IN TERMS OF OHMS. THE OHMMETER IS GENERALLY
MADE MULTIRANGE INSTRUMENT BY USING DIFFERENT VALUES OF R.

10. APPLICATIONS OF MULTIMETER
• A MULTIMETER IS AN EXTREMELY IMPORTANT ELECTRONIC
INSTRUMENT AND IS EXTENSIVELY USED FOR CARRYING OUT
VARIOUS TESTS AND MEASUREMENTS IN ELECTRONIC CIRCUITS.
IT IS USED :
– FOR CHECKING THE CIRCUIT CONTINUITY. WHEN THE MULTIMETER
IS EMPLOYED AS CONTINUITY CHECKING DEVICE, THE OHMMETER
SCALE IS UTILISED AND THE EQUIPMENT TO BE CHECKED IS SHUT OFF
OR DISCONNECTED FORM THE POWER MAINS.
– FOR MEASURING DC CURRENT FLOWING THROUGH THE CATHODE,
PLATE, SCREEN AND OTHER VACUUM TUBE CIRCUITS.
– FOR MEASURING DC VOLTAGES ACROSS VARIOUS RESISTORS IN
ELECTRONIC CIRCUITS.
– FOR MEASURING AC VOLTAGE ACROSS POWER SUPPLY
TRANSFORMERS.
– FOR MEASURING WHETHER OR NOT OPEN OR SHORT CIRCUIT EXISTS
IN THE CIRCUIT UNDER STUDY.

11. SENSITIVE OF MULTIMETER
• THE RESISTANCE OFFERED PER VOLT OF FULL SCALE
DEFLECTION BY THE MULTIMETER IS KNOWN AS
MULTIMETER SENSITIVITY. MULTIMETER SENSITIVITY
INDICATES THE INTERNAL RESISTANCE OF THE MULTIMETER.
• Example
– If the total resistance of the meter is 5000 ohms and the meter is to
read 5 volts full scale, then internal resistance of the meter is 100 ohm
per/volt i.e. meter sensitivity is 1000 ohm per volt. Conversely, if the
meter sensitivity is 400 ohm per volt which reads from 0 to 100 v, then
meter resistance is 40000 ohms. If the meter is to read V volts and Ig
is the full scale deflection current then,
• Meter resistance = V/Ig
• Meter sensitivity = Resistance per volt full scale
deflection

12. Example
If the total resistance of the meter is 5000 ohms and the meter is to
read 5 volts full scale, then internal resistance of the meter is 100 ohm
per/volt i.e. meter sensitivity is 1000 ohm per volt. Conversely, if the
meter sensitivity is 400 ohm per volt which reads from 0 to 100 v, then
meter resistance is 40000 ohms. If the meter is to read V volts and Ig is
the full scale deflection current then,
Meter resistance = V/Ig
Meter sensitivity = Resistance per volt full scale deflection
= v/Ig /V = 1/Ig

13. CATHODE RAY OSCILLOSCOPE
• CRO IS AN ELECTRONIC DEVICE WHICH IS CAPABLE OF
GIVING A VISUAL INDICATION OF A SIGNAL WAVEFORM.
NO OTHER INSTRUMENT USED IN THE ELECTRONIC
INDUSTRY IS AS VERSATILE AS THE CATHODE RAY
OSCILLOSCOPE. IT IS WIDELY USED FOR TROUBLE
SHOOTING RADIO AND TELEVISION RECEIVERS AS WELL
AS FOR LABORATORY WORK INVOLVING RESEARCH AND
DESIGN. WITH A OSCILLOSCOPE, THE WAVE SHAPE OF A
SIGNAL CAN BE STUDIED WITH RESPECT TO AMPLITUDE
DISTORTION AND DEVIATION FROM THE NORMAL. IN
ADDITION, THE OSCILLOSCOPE CAN ALSO BE USED FOR
MEASURING VOLTAGE, FREQUENCY AND PHASE SHIFT.

14. CATHODE RAY TUBE (CRT)
• IT DISPLAYS THE QUANTITY BEING MEASURED.
IT IS THE ‘HEART’ OF AN OSCILLOSCOPE AND VERY
SIMILAR TO THE PICTURE TUBE IN A TELEVISION SET.
ITS FOUR MAJOR COMPONENTS ARE :-
(a)AN ELECTRON GUN - FOR PRODUCING A STEAM OF
ELECTRONS ,
(b)FOCUSSING AND ACCELERATING ANODES
(c ) HORIZONTAL AND VERTICAL DEFLECTING PLATES
(D) AN EVACUATED GLASS ENVELOPE WITH A
PHOSPHORESCENT SCREEN WHICH PRODUCES BRIGHT
SPOT

15. CATHODE RAY TUBE (CRT)
• IT DISPLAYS THE QUANTITY BEING MEASURED.
IT IS THE ‘HEART’ OF AN OSCILLOSCOPE AND VERY
SIMILAR TO THE PICTURE TUBE IN A TELEVISION SET.
ITS FOUR MAJOR COMPONENTS ARE :-
(a)AN ELECTRON GUN - FOR PRODUCING A STEAM OF
ELECTRONS ,
(b)FOCUSSING AND ACCELERATING ANODES
(c ) HORIZONTAL AND VERTICAL DEFLECTING PLATES
(D) AN EVACUATED GLASS ENVELOPE WITH A
PHOSPHORESCENT SCREEN WHICH PRODUCES BRIGHT
SPOT

16. NORMAL POSITION OF (CRT)
• THEC SIGNAL TO BE VIEWED OR DIAPLAYED ON THE SCREEN
IS APPLIED ACROSS THE y- PLATES OF A CRT.BUT SEE ITS
WAVEFORM OR PATTERN ,IT IS ESSENTIAL TO SPERED IT OUT
HORIZONTALLY FROM LEFT RIGHT.THE ELECTRON BEAM
WOULD MOVE UNIFORMLY FROM LEFT TO RIGHT THEREBY
GRAPHING VERTICAL VARIATIONS OF THE INPUT SIGNAL
VERUS TIME.DUE TO REPETITIVE TRACING OF THE VIEWED
WAVEFORM,WE GET CONTINUOUS OF VISION.HOWEVER .FOR
GETTING A STATIONARY ON THE SCREEN.IT IS ESSENTIAL TO
SYACHRONIZE THE HORIZONTAL SWEEPING OF THE
BEAM(SYNC) WITH THE INPUT SIGNAL WILL BE PROPERLY
SYNCED ONLY WHEN ITS FREQUENCY EQUALS THE SWEEP –
GENERATOR FREQUENCY .

17. POWER SUPPLY
(a) Intro to power supplies.
(b) Half wave rectifier.
(c) Full wave rectifier.
(d) Bridge rectifier.
(e) Filter cct
(f) Voltage multiplier.
(g) DC to DC converters.
(h) Voltage regulator.

18. INTRODUCTION
In general, electronic circuits require a source
of a DC power. The Btys are rarely used for the
purpose as they are costly and require frequent
replacement. In practice, DC power for electronic
cct is most conveniently obtained from commercial
AC lines by using rectifier, filter system, called a
DC power supply

19. BLOCK DIAGRAM OF POWER
SUPPLY
TRANSFORMER RECTIFIER FILTER REGULATOR
ISOLATION & HALF WAVE, CAPACITOR, ZENOR,
FULL WAVE
STEP UP, CHOKE & GAS TUBE &
(a) CENTRE TAP
STEP DOWN π TYPE SCR
(b) BRIDGE RECT.
PULSATING D.C. PURE D.C.
A.C. D.C. CONSTANT

20. ‘BLOCK DIGRAM OF HALF
WAVE RECTIFIER
D
A V
1
OUT
A.C. RL
SUPPL
Y t
B

21. CENTRE TAP FULL WAVE
RECTIFIER
A
D
V
1
OUT
RL
A.C.
O D D
D D
SUPPL
Y t
1 2 1 2
B D
2

22. BLOCK DIAGRAM BRIDGE
RECTIFIER
P
D D
1 4
A.C. B
SUPP
LY
RL V
D
D OUT
) 2
3
Q

23. RECTIFIER
• IT IS A CIRCUIT WHICH EMPLOYS ONE OR MORE DIODES TO
CONVERT A.C. VOLTAGE .
FILTER
THE FUNCTION OF THIS CIRCUIT ELEMENT IS TO REMOVE
THE FLUCTUATIONS OR PLUSATIONS (CALLED RIPPLES)
PRESENT IN THE OUTPUT VOLTAGE SUPPLIED BY THE
RECTIFIER. OF COURSE, NO FILTER CAN, IN PRACTICE, GIVE
AN OUTPUT VOLTAGE AS RIPPLE- FREE AS THAT OF A D.C.
BATTERY, BUT IT APROACHES IT SO CLOSELY THAT THE
POWER SUPPLY PERFORMS AS WELL.
VOLTAGE REGULATOR
ITS MAIN FUNCTION IS TO KEEP THE TERMINAL
VOLTAGE OF THE D.C. SUPPLY CONSTANT EVEN WHEN:-

24.  A.C INPUT TO THE TRANSHORMER VARIES (DEVIATIONS FROM 22V
ARE COMMON) .
 THE LOAD VARIES.
 USAUALLY, ZENER DIODES AND TRANSISTORS ARE
USED FOR VOLTAGE REGULATION PURPOSE . AGAIN, IT
IS IMPOSSIBLE TO GET 100% CONSTANT VOLTAGE BUT
MINOR VARIATIONS ARE ACCEPTABLE FOR MOST OF
THE JOBS.
POWER SUPPLY
 UNREGULATED POWER SUPPLY : - AN
UNREGULATED POWER SUPPLY WHOSE TERMINAL D.C.
VOLTAGE IS AFFECTED SIGNIFICANTLY BY THE
AMOUNT OF LOAD. AS THE LOAD DRAWS MORE
CURRENT, THE D.C. TERMINAL VOLTAGE BECOMES
LESS.

25.  REGULATED POWER SUPPLY : -
IT IS THAT D.C. POWER SUPLLY WHOSE
TERMINAL VOLTAGE REMAINS ALMOST
CONSTANT REGARDLESS OF THE AMOUNT
OF CURRENT DRAWN IT. AN UNREGULATED
SUPLY A CAN BE CONVERTED INTO A
REGULATED POWER SUPPLY BY ADDING A
VOLTAGE CIRCUIT IT.
 TRANSFORMER : - ITS JOB IS
EITHER TO STEP UP OR MOSTLY STEP
DOWN THE A.C. SUPPLY VOLTAGE TO SUIT
THE RECUIREMENT OF THE SOLID- STATE
ELECTRONIC DEVICES AND CIRCUITS FED
BY THE D.C. POWER SUPLY. IT ALSO
PROVIDES ISOLATION FROM THE SUPPLY
LINE-AN IMPORTANT SAFETY
CONSIDERATION.

26. FILTERS
THE MAIN FUNCTION OF A FILTER
CIRCUIT IS TO MINIMIZE THE RIPPLE THE
CONTENT IN THE RECTIFIEROUTPUT.
V1
in FILTER
out
t
PULSATING Filtered D.C.
D.C.

27. SERIES INDUCTOR FILTER
L
FROM
RECTIFIER
FILTER
HALF-
CIRCUIT
WAVE
OUTPUT
VL
IL

28. THE CLS OR π FILTER
L
FROM
RECTIFIER RL
C1 C2

29. VOLTAGE MULTIPLIER
 HALF WAVE VOLTAGE DOUBLER
FULL WAVE VOLTAGE DOUBLER
VOLTAGE TRIPLER
VOLTAGE DIVIDER

30. HALF WAVE VOLTAGE DOUBLER
D2
+ - Vi
-
C1
-
VM VL= 2VM
D1 + C2
VL
+
2VM
t

31. FULL WAVE VOLTAGE DOUBLER
TRIPLER (3 VM)
VM 2VM
+ + - + -
C1 C3
VM
- D1 D2 D3 D4
O t
C2
- + - + -
2VM 2VM
DOUBLER (2 VM)
QUADRUPLER (4 VM)

32. DC TO DC CONVERTER
Sometimes we want to convert a DC voltage to another DC voltage
of a different value. If we have a system with a positive supply of
+5V, can use a DC to DC converter to produce an output of +15V.
All kind of designs are possible for DC to DC converters. In this
section, we discuss a hypothetical design to get an idea of how a
DC to DC converter works.
Basic Idea.
In most DC to DC converters, the input DC voltage is applied to a
square wave oscillator whose output drives a transformer, as
shown in fig. The frequency, the smaller the transformer and filter
components.
+ +
RECTIFIER
V IN OSCILLATOR V OUT
& FILTER
- -

33. VOLTAGE REGULATORS
A device which maintains the output voltage of an ordinary
power supply constant irrespective of load variations or changes
in in put AC voltage is known as a voltage regulator. A voltage
regulator generally employs electronic device to achieve this
objective. There are basic two types of voltage regulators:-
(a) Series voltage regulator.
(b) Shunt voltage regulator.
V in
Series Regulator
RS
SHUNT
LOAD
LOAD V out REGULATOR V out

34. ZENER DIODE VOLTAGE REGULATOR
When the zener diode is operated in the breakdown or
zener region, the voltage across it is substantially
constant for a large change of current through it.
+ Rs IL
I
Iz
(unregulated DC) Vz
V out
-

35. TRANSDUCER
(a) Intro and charters of transducer.
(b) Types of transducer.
(c) Termester & its characteristics.
(d) RTD & its characteristics.

36. WHAT IS A TRANSDUCER ?
IN GENERAL TERMS,A TRANSDUCER MAY BE DEFINED AS ANY DEVICE
THAT CONVERTS IN ONE FORM ENERGY IN TO ANOTHER FORM.
MOST OF THE TRANSDUCERS EITHER CONVERT ELECTRICAL
ENERGY INTO MECHANICAL DISPLACEMENT AND /OR CONVERT SOME
NON-ELECTRICAL PHYSICAL QUANTITY<SUCH AS
TEMPARATURE,LIGHT,FORCE,SOUND,ETC.> TO AN ELECTRICAL
SIGNAL.
IN AN ELECTRONIC INSTRUMENTATION SYSTEM,THE FUNCTIONS OF A
TRANSDUCER <BEING THE INPUT DEVICE>ARE TWO –FOLD:-
<i> TO DETECT OR SENSE THE PRESENCE MAGNITUDE&CHANGES IN
THE PHYSICAL QUANTITY BEING MEASURED.
<ii> TO PROVIDE A PROPORTIONAL ELECTRICAL OUTPUT SIGNAL AS
SHOWN IN FIGURE.
z
TRANSDUCER
PHYSICAL QUANTITY ELECTRICAL OUTPUT
EXCITATION

37. CLASSIFICATION OF TRANSDUCERS
TRANSDUCERS MAY BE CLASSIFIED ACCORDING TO THEIR
APPLICATIONS , METHOD OF ENERGY CONVERSION ELECTRICAL
MEASURING PRINCIPLE INVOLVED,NATURE OF OUTPUT SIGNAL
AND SO ON.
BROADLY SPEAKING ,TRANSDUCES MAY BE CLASSIFIED INTO
THE FOLLOWING TWO GROUPS:-
1. PASSIVE TRANSDUCERS - THEY REQUIRE AN EXTERNAL POWER
SUPPLY AND THEIR OUTPUT IS A MEASURE OF SOME VARIATION
IN A PHYSICAL PARAMETER SUCH AS PRESSURE ,RESISTANCE
AND CAPACITANCE ETC.
2. SELF-GENERATING TRANSDUCERS – THEY DO NOT REQUIRE AN
EXTERNAL POWER SOURCE. HOWEVER,THEY PROVIDE AN
ELECTRICAL OUTPUT WHEN STIMULATED BY SOME PHYSICAL
FORM OF ENERGY.

38. A VERY USEFUL LISTING OF DIFFERENT TRANSDUCERS IS
GIVEN BELOW :-
1.MECHANICAL - STRAIN GUAGE TYPE FOR MEASURING,
FORCE ,TORQUE & PRESSURE ETC.
2. THERMAL - THEMISTORS,THERMOCOUPLES.
3. OPTICAL - PHOTOCONDUCTIVE,PHOTOEMISSIVE &
PHOTOVOLTAIC <SOLAR>CELLS.
4. ACOUSTICAL - MICROPHONE
5. MAGNETIC -LVDT,PERMEATERS
6. CHEMICAL - PH & CONDUCTIVITY CELLS
7. NUCLEAR - GIEGER-MULLER TUBE,IONIZATION
CHAMBER .
8. BIOLOGICAL -ELECTROCARDIOGRAPH (ECG) AND
ELECTROENCE PHALOGRAPH (EEG).

39. DECIMAL TO BCD ENCODER
+δv
0
1
2
3
4
5
6
7
8
9
A B C D

40. THERMISTOR
• IT IS A TEMPERATURE-SENSITIVE SEMICONDUCTOR WITH A
HIGH NEGATIVE TEMPERATURE CO-EFFICIENT OF
RESISTACE
• IT MEASURE THE VALUE OF TEMPERATURE IN BETWEEN
-100*C TO + 350*C

41. THERMISTOR AND ITS APPLICATIONS
• ALONGWITH A WHEATSTONE BRIDGE CIRCUIT
• THERMISTOR ARE USED TO MEASURING TEMPERATURE,
THERMAL CONDUCTIVITY,
• ATTITUDE AND WIND VELOCITY

42. THERMISTORS
THERMISTORS ARE SEMICONDUCTORS, MADE FROM A SPECIFIC
MIXTURE OF PURE OXIDES OF NICKEL, MANGANEE, COPPER, COBALT,
IRON, MAGNESIUM, TITANIUM & OTHERR METALS SINTERED AT
TEMPERATURES ABOVE 982°C. THEIR DISTINGUISHING
CHARACTERISTICS ARE A HIGH TEMPRATURE COEFFICIENT, USAULLY
NEGATIVE, ALTHOUGH IT CAN BE POSITIVE AS WELL, AND THE FACT THAT
THEIR RESISTANCE IS A FUNCTION OF ABSOLUTE TEMPRATURE.
THERMISTORS WERE RECOGNIZED IN THE EARLY 1800, BUT THEIR USE
WAS FIRDT INTRODUCED BY BELL LABORATORIES IN ABOUT 1940,
NAMING THEM FROM “THE TERM THERMALLY SENSITIVE RESISTORS”.
ADVANTAGES :
(i) (i) SMALL SIZES AND FAST RESPONSE
(ii) (ii) SUITABILITY FOR NARROW SPANS. (iii) LOW COST
(iii) (iv) SENSOR EXHIBITING A GRETER SESITIVITY AS THE TEMPERATURE
DROPS, WHEN TEMPRATURE CO-EFFICIENT IS NEGATIVE.
(v) DUE TO THE LARGE SENSOR (THERMISTOR) RESISTANCE, THE
CONTACT OR LEAD-WIRE RESISTANCE CONSIDERED AS NECLIGIBLE.
DISADVANTAGES :
(i) VERY NON-LINER TEMPRATURE VERSUS RESISTANCE CURVS.
(ii) UNSUITABILITY FOR WIDE TEMPRATURE SPANS.
(iii) PROBLEM DUE TO INTERCHANGEABILITY OF INDIVIDUAL ELEMENT.
(iv) DOUBTFUL, STABILITY AT HIGHERTEMPRATURE )

43. RTD IS USED FOR
• MEASUREMENT OF TEMPERATURE RANGE 180*C TO 650 *C
• THE IMMERSION IN THE MEDIUM WHOSE TEMPERATURE IS TO
BE MEASURED
• FOR INDUSTRIAL PURPOSES

44. RESISTACE TEMPERATURE
DETECTOR
• RTDs ARE MADE OF A SUITABLE LENGTH OF
PLATINUM,NICKEL OR TUNGSSTEN WIRE WHOSE
RESISTANCE INCREASES WITH INCREASE IN TEMPERATURE
• WHICH HAS POSITIVE TEMPERATURE COEFFICIENT
• THE RELATIONSHIP BETWEEN TEMPERATURE AND
RESISTACE

45. THERMOCOUPLES
THE WORKING PRINCIPLE OF A
THERMOCOUPLE DEPENDS ON THE THERMO-
ELECTRIC EFFECT. IF TWO DISSIMILAR METALS
ARE JOINED TOGETHER SO AS TO FORM A
CLOSED CIRCUIT, THERE WILL BE TWO
JUNCTIONS IS HEATED, THEN, A CURRENT
FLOWS IN THE CIRCUIT WHICH CAN BE
DETECTED BY A GALVANOMETER. THE AMOUNT
OF THE CURRENT PRODUCED DEPENDS ON THE
DIFFERENCE IN THE TEMPERATURE BETWEEN
THE TWO JUNCTIONS AND ON THE
CHARACTERISTICS OF THE TWO METALS. THIS
WAS FIRST OBSERVED BY SEE BACK IN 1821 AND
IS KNOWN AS SEE BECK EFFECT.

46. THERMOCOUPLE
DISSIMILAR METAL
WIRES
REFRENCE
JUNCTION
COLD
MEASURING
JUNCTION
(HOT) HEAT
SOURCE
ISA TYPE POSITIVE WIRE POSITIVE WIRE MILLIVOLTS / °C RECOMMENDE TEMP (°C)
DESIGNATION NUMBERS NUMBERS (MIN TO MAX) Min MAX
0.0527 TO0.05745
J IRON -196 760
0.041 TO 0.040
K CHROMEL -190 1371
0.00645 TO 0.0118
R PT 87-RH 13 -18 1704
0.00643 TO 0.01056
S PT 90-RH 10 -18 1760
0.04277 TO 0.052
T COPPER -190 390

47. CLASSIFICATION BASED ON ELECTRICAL
PRINCIPAL INVOLVED
A BETTER WAY OF CLASSIFYING TRANSDUCERS IS TO ARRANGE
THEM ACCORDING TO THE BASIC ELECTRICAL MEASURING
PRINCIPLE INVOLVED IN CONVERTING THE PHYSICAL QUANTITY
(OR ITS VARIATIONS) IN TO CORRESPONDING ELECTRICAL
QUANTITY (OR VARIATIONS). SUCH AS ARRANGEME
NT IS GIVEN BELOW;
(a). VARIABLE-RESISTANCE TYPE
1. STRAIN AND PRESSURE GAUGES,
2. THERMISTORS, RESISTANCE THERMOMETERS.
3. PHOTOCONDUCTIVE CELL.
4. CHEMICAL CONDUCTIVE METER.
5. CONTACT THICKNESS GAUGE ETC.
(b).VARIABLE-INDUCTANCE TYPE
1. LINEAR VARIABLE DIFFERENTIAL TRANSFORMER(LVDT)
2. RELUCTANCE PICK-UP
3. EDDY CURRENT GAUGE

48. (C). VARIABLE –CAPACITANCE TYPE :-
1. CAPACITOR MICROPHONE
2. DIELECTRIC GUAGE
3. PRESSURE GUAGE
(D) VOLTAGE-DIVIDER TYPE :-
1. POTENTIOMETER POSITION SENSOR
2. PRESSURE ACTUATED VOLTAGE DIVIDER
(E) VOLTAGE GENERATING TYPE :-
1. PIEZOELELECTRIC PICK-UP
2. THERMOCOUPLE
3. PHOTOVOLTAIC (SOLAR) CELL,
4. ROTATIONAL MOTION TACHOMETER

49. THIS VARIES RESISTANCE OF THE MICROPHONE IN STEP WITH
THE VARIATIONS IN THE INCIDENT SOUND WAVES.IF THE
MICROPHONE IS CONNECTED IN A CIRCUIT (FIG)CONTAINING A
BATTERY AND A COIL,THEN THE CURRENT IN THE CIRCUIT VARIES
ACCORDING TO THE CHANGE IN THE SPEECH.THESE VARIATIONS
IN THE CIRCUIT CURRENT SETUP AN INDUCED E.M.F IN THE COIL L 1
WHICH MAY BE FURTHER STEPPED UP WITH THE HELP OF A
TRANSFORMER.
IT MAY BE NOTED THAT THE METAL DIAPHRAM HAS TO BE
SUITABLY DAMPED BY COTTON WOOL IN ORDER TO AVOID
PROMINENT RESONANCE EFFECTS.SUCH MICROPHONES ARE NON-
DIRECTIONAL IN NATURE, HAVE GOOD FREQUENCY RESPONSE
AND GIVE CONSIDERABLE OUTPUT.HOWEVER,THEY HAVE THE
FOLLOWING SERIOUS DRAWBACKS.
1. THEY ARE NOISY I.E THEY GENERATE AN OBJECTIONABLE
BACKGROUND HISS (SIMILAR TO THE FRYING NOISE).
2. THEY ARE NOT SUITABLE FOR HIGH –QUALITY REPRODUCTION.
3. THEY SUFFER FROM ANOTHER DEFECT KNOWN AS PACKING I.E
CLINGING TOGETHER OF THE GRANULES DUE TO THE PRESENCE
OF MOISTURE.THIS REDUCES THE RESISTANCE OF THE
MICROPHONE AND RENDERS IT SENSITIVE.

50. RIBBON MICROPHONE
IT IS ALSO KNOWN AS VELOCITY MICROPHONE AND CONSISTS OF
A THIN ,STRETCHED DURALUMIN RIBBON APPROXIMATELY 6MM WIDE
AND50 TO 100MM LONG (OF 1Ω RESISTANCE) SUSPENDED BETWEEN THE
POLES OF A PERMANENT MAGNET. THE RIBBON IS CLAMPED ONLY AT
ITS ENDS AND ,BUT FOR THESE ENDS,IS FREE TO MOVE BACK AND
FORTH IN THE MAGNETIC FIELD PROVIDED BY THE PERMANENT
MAGNET.
WHEN SOUND WAVES FALL ON THE MAGNETIC RIBBON ,IT MOVES
IN AND OUT OF THE MAGNETIC FIELD.DUE TO THE CUTTING OF THE
MAGNETIC FLUX,AN INDUCED EMF IS PRODUCED IN THE RIBBON
WHOSE FREQUENCY CORRESPONDS TO THAT OF THE INCIDENT
SOUND.IN THIS WAY,ACOUSTIC ENERGY IS CONVERTED INTO
ELECTRICAL ENERGY.
BECAUSE OF THE LOW MICROPHONE RESISTANCE (ABOUT 1Ω), A
STEP-UP TRANSFORMER IS MOUNTED IN THE MIKE CASE ITSELF.THIS
TRANSFORMER SERVES TWO PURPOSES (i) FIRSTLY,WHILE ACTING AS
AN IMPEDANCE MATCHING TRANSFORMER,IT INCREASES MIKE
IMPEDANCE TO ABOUT 200Ω THUS ENABLING ITS DIRECT CONNECTION
TO A PREAMPLIER WHICH HAS NEARLY THE SAME INPUT IMPEDANCE
(ii) SECONDLY,IT STEPS UP THE OUTPUT VOLTAGE OF THE MIKE.

51. A RIBBON MIKE IS SENSITIVE ONLY TO SOUNDS COMING
FROM THE FRONT OR BACK BUT NOT FROM SIDES,SUCH
MICROPHONES HAVE :-
 EXCELLENT HIGH-FREQUENCY RESPONSE.
 FLAT RESPONSE OVER AUDIO RANGE,
 A SMOOTHER RESPONSE THAN MOVING –COIL MIKES,
 GENTLE TREBBLE ROLL - OFF, AND
 NO ‘POPPING’ PROBLEM

52. MOVING – COIL MICROPHONE
THOUGH BOTH RIBBON MICROPHONE AND MOVIN- COIL
MICROPHONE BELONG TO THE CATEGORY PF DYNAMIC
MICROPHONES,USUALLY THE WORD ‘DYNAMIC’AND ‘MOVING
COIL’ HAVE BECOME SYNONYMOUS .
IT CONSISTS OF A LIGHT DIAPHRAM SHAPED LIKE A
HOLLOW CONE WHICH IS CLAMPED TO A CASE AROUND ITS
OUTER RIM AS SHOWN IN FIGURE.
THE DIAPHRAM IS MADE EITHER OF STIFF CARDBOARD
OR FIBRE (OR MORE RECENTLY , OF PLASTIC
MATERIALS)AND HAS CIRCULAR CORRUGATIONS PRESSED
INTO IT.THIS MAKES IT VERY SPRINGLY AND ALTHOUGH IT IS
CLAMPED AT THE EDGES, YET EVEN A SLIGHPRESSURE
APPLIED AT ITS CENTRE CAN MAKE IT MOVE IN AND
OUT.WHEN SOUND WAVES FALL ON IT.THEN DUE TO
VARIATIONS IN THE PRESSURE OF THE WAVES,THE
DIAPHRAM MOVES IN AND OUT.SINCE THE DIAPHRAM IS
LIGHT ABD HIGHLY FLEXIBLE.ITS VIBRATORY MOTION IS
MORE OR LESS FAITHFUL REPRODUCTION OF THE SOUND
WAVE FORM.

53. TO THE REAR OR BACK SIDE OF THE DIAPHRAM IS
ATTACHED A VERY LIGHT CYCLINDRICAL FORMER OF AN
INSULATING MATERIAL ON WHICH IS WOUND THE COIL C
HAVING MANY TURNS OF FINE WIRE.THE FORMER, ALONG
WITH COIL,FITS INTO THE GAP OF AN ANNULAR MAGNET.
WHEN THE SOUND WAVES FALL ON THE DIAPHRAM,IT
VIBRATES IN AND OUT.THE COIL ATTACHED TO ITS REAR
ALSO MOVES IN AND OUT IN THE STRONG MAGNETIC FIELD
THERE BY CUTTING THE MAGNETIC FLUX.HENCE,AN
OSCILLATORY E.M.F IS INDUCED IN THE COIL C WHOSE
MAGNITUDE DEPENDS ON THE QUICKNESS OF THE MOVEMENT
OF THE COIL.THIS OSCILLATORY E.M.F WHICH REPRESENTS
THE SOUND WAVES, CAN BE AMPLIFIED FURTHER FOR
DRIVING A LOUDSPEAKER ETC.
MOVING –COIL MICROPHONES ARE WIDELY USED BECAUSE
THEY:-
1. ARE DEPENDABLE ,RUGGED AND HAVE MOST RELIABLE
DESIGN FOR BOTH INDOOR AND OUTDOOR WORK.
2. HAVE THE SMOOTHEST AND MOST EXTENDED FREQUENCY
RESPONSE AS COMPARED TO CARBON,CRYSTAL AND
CERAMIC MIKES.
3. PROVIDE MUCH HIGHER OUTPUT SIGNAL VOLTAGE FOR A
GIVEN SOUND PRESSURE INPUT THAN THE RIBBON MIKES.
4. ARE QUITE SUITABLE FOR HIGH QUALITY REPRODUCTION.

54. CRYSTAL MICROPHONE
THE ACTION OF SUCH MIROPHONE DEPENDS ON THE
PIEZOELECTRIC EFFECT EXHIBITED BY CRYSTALS OF
QUARTZ,TOURMALINE AND ROCHELLE SALT. SUCH
CRYSTALS DEVELOP A POTENTIAL DIFFERENCE ACROSS
THEIR OPPOSITE FACES WHEN SUBJECTED TO MECHANICAL
DEFORMATION SUCH AS SQUEEZING,TWISTING OR
BENDING .THE MAGNETUDE OF THE VOLTAGE DEVELOPED IS
PROPORTIONAL TO THE EXTENT OF THE DEFORMATION
PRODUCED AND ITS POLARITY IS REVERSED WHEN THE
DIRECTION OF THE DEFORMING FORCE IS REVERSED . FOR
EXAMPLE ,IF THE VOLTAGE PRODUCED BY THE CRYSTAL IS
POSITIVE WHEN TWISTED CLOCKWISE,THEN IT WOULD BE
NEGATIVE WHEN TWISTED ANTICLOCKWISE.
ROCHELLE SALT CRYSTAL IS USED FOR AUDIO-
FREQUIENCIES WHEREAS QUARTZ CRYSTAL IS USED FOR
HIGH FREQUENCIES UP TO MANY MEGAHERTZ (MHZ)

55. AS SHOWN IN FIGURWE ,THE CENTRE OF THE
DIAPHRAM IS ATTACHED TO A DRIVE PIN WHOSE OTHER END
CONTACTS A SANDWICH OF METAL PLATES WHICH CONTAIN
THE CRYSTAL.THE LOWER END OF THE METAL SANDWICH IS
FIXED TO THE MICROPHONE HOUSING BUT THE UPPER END
IS FREE TO MOVE.WHEN SOUND WAVES FALL ON THE
DIAPHRAM ,IT VIBRATES TO AND FRO THEREBY
SUBJECTING THE CRYSTAL TO MECHANICAL
STRESS.HENCE,AN ALTERNATING VOLTAGE IS DEVELOPED
BETWEEN THE OPPOSITE FACES OF THE CRYSTAL.THIS
VOLTAGE IS PICKED UP BY METAL PLATE ELECTRODES
(MARKED E) AND THEN TAKEN OUT FOR FURTHER
NECESSARY AMPLIFICATION.
IN SOME TYPES OF MICROPHONES ,THE CRYSTAL SLAB
ACTDS AS ITS OWN DIAPHRAM BUT MORE SLABS ARE
NECESSARY IN THAT CASE.

56. SUCH MICROPHONES SUFFER FROM MECHANICAL
RESONANCE OF THE DIAPHRAM AND THEIR VOLTAGE FALLS
OFF VERY RAPIDLY AT HIGHER FREQUENCIES.ALSO, THE
ELECTRICAL WAVEFORM GENERATED BY THEM IS NOT A VERY
FAITHFUL COPY OF THE WAVEFORM OF MECHANICAL
DEFORMATION APPLIED TO THEM.THEY ARE NOT USEFUL FOR
RECORDING WORK BUT ARE ONLY USED IN VOICE
COMMUNICATION WHERE MAIN OBJECTIVE IS INTELLIGIBILITY
OF SOUND.THE CRYSTAL CAN BE EASILY DAMAGED BY
TEMPARATURE AND HUMIDITY.HOWEVER,ONE OF THEIR
OUTSTANDING FEATURE IS THAT THEY GIVE VERY LARGE
OUTPUT FOR A GIVEN SOUND INPUT AND SO NEEDLESS
SUBSEQUENT AMPLIFICATION AS COMPARED TO OTHER
MICROPHONES .SINCE THEIR IMPEDANCE IS HIGH,THEY CAN
BE DIRECTLY CONNECTED TO THE HIGH INPUT IMPEDANCE OF
AN AMPLIFIER.THEY CAN BE MADE SMALL ENOUGH TO BE
USED IN HEARING AIDS.

57. CERAMIC MICROPHONE
IN THIS MICROPHONE, THE TRANSDUCER ELEMENT IS
BARIUM TITANATE (A CERAMIC) WHICH HAS PIEZOELECTRIC
PROPERTIES.HENCE ,IT IS JUST LIKE A CRYSTAL
MICROPHONE EXCEPT THAT IT HAS
 BETTER TOLERANCE AS REGARDS HEAT AND HUMIDITY.
 SLIGHTLY HIGHER SIGNAL OUTPUT FOR THE SAME
SOUND INPUT.

58. CAPACITOR MICROPHONE
THE TRANSDUCER USED IN MIKE IS A PARALLEL-PLATE
CAPACITOR WHOSE ONE PLATE IS VARIABLE(ART .36.7). THE
CAPACITOR IS KEPT CHARGED TO A CERTAIN POTENTIAL
DIFFERENCE BY A DC VOLTAGE CALLED POLARIZING
VOLTAGE.WHEN SOUND FALLS ON SUCH A CAPACITOR,ITS
MOVABLE PLATE VIBRATES TO AND FRO. AS IT MOVES
INWARDS,CAPACITANCE C INCREASES AND HENCE
INCREASES ITS CHARGING ABILITY.OPPOSITE CONDITION
PREVAILS WHEN THE PRESSURE VARIATIONS OF THE
INCIDENT SOUND.THESE VOLTAGE VARIATIONS CAN BE
AMPLIFIED TO A

59. LEVEL HIGH ENOUGH TO SUPPLY SUFFICIENT CURRENT FOR
RECORDING ON MAGNETIC TAPE. SUCH MICROPHONES HAVE :-
1. EXTREMELY HIGH IMPEDANCE (10MΩ) AND HAVE BUILT-IN
AMPLIFIER TO AVOID THE USE OF CONNECTING CABLE,
2. EXCELLENT FREQUENCY RESPONSE.
3. LOW DISTORTION,
4. EXCELLENT TRANSIENT RESPONSE DUE TO THE EXTREMELY
SMALL MASS OF THEIR MOVING PLATE (i.e DIAPHRAM)

60. THE ELECTRET MICROPHONE
IT IS SIMILAR TO A CAPACITOR MICROPHONE EXCEPT
THAT IT DOES NOT REQUIRE A POLARIZING VOLTAGE FOR
ITS CAPACITOR.ITS TRANSDUCER ELEMENT IS A SELF-
POLARIZED CAPACITOR CALLED ELECTRET CAPACITOR.IT
IS A SPECIALLY-DESIGNED CAPACITOR WHICH ONCE
CHARGED DURING ITS MANUFACTURE, HOLDS ITS CHARGE
IN-DEFINITELY THEREBY ELIMINATING THE NEED FOR A
POLARIZING VOLTAGE SOURCE.

61. SINUSOIDAL OSCILLATOR
AN ELECTRONIC DEVICE THAT GENERATES SINUSOIDAL
OSCILLATIONS OF DESIRED FREQUENCY IS KNOWN AS A
“SINUSOIDAL OSCILLATOR”.
TYPES OF SINUSOIDAL OSCILLATIONS :-
SINUSOIDAL OSCILLATIONS
CAN BE OF TWO TYPES VIZ DAMPED OSCILLATIONS AND
UNDAMPED OSCILLATIONS.
<1> DAMPED OSCILLATIONS :- THE ELECTRICAL OSCILLATIONS
WHOSE AMPLITUDE GOES ON DECREASING WITH TIME ARE
CALLED DAMPED OSCILLATIONS.
<2> UNDAMPED OSCILLATIONS :-THE ELECTRICAL OSCILLATIONS
WHOSE AMPLITUDE REMAINS CONSTANT WITH TIME ARE CALLED
UNDAMPED OSCILLATIONS.
OSCILLATORY CIRCUIT :- A CIRCUIT WHICH PRODUCES
ELECTRICAL OSCILLATIONS OF ANY DESIRED FREQUENCY IS
KNOWN AS “OSCILLATORY CIRCUIT OR TANK CIRCUIT.”

62. ESSENTIALS OF TRANSISTOR OSCILLATOR:
<1> TANK CIRCUIT :- IT CONSISTS OF INDUCTANCE COIL (L)
CONNECTED IN PARALLEL WITH CAPACITOR (C),THE
FREQUENCY OF OSCILLATIONS IN THE CIRCUIT DEPENDS
UPON THE VALUES OF INDUCTANCE OF THE COIL AND
CAPACITANCE OF THE CAPACITOR.
<2> TRANSISTOR AMPLIFIER :- THE TRANSISTOR AMPLIFIER
RECIEVES D.C POWER FROM THE BATTERY AND CHANGES IT
INTO A.C POWER FOR SUPPLYING TO THE TANK CIRCUIT.THE
OSCILLATIONS OCCURING IN THE TANK CIRCUIT ARE APPLIED
TO THE INPUT OF THE TRANSISTOR AMPLIFIER.BECAUSE OF
THE AMPLIFYING PROPERTIES OF THE TRANSISTOR,WE GET
INCREASED OUTPUT OF THESE OSCILLATIONS.THIS AMPLIFIED
OUTPUT OF OSCILLATIONS IS DUE TO THE D.C POWER
SUPPLIED BY THE BATTERY.THE OUTPUT OF THE TRANSISTOR
CAN BE SUPPLIED TO THE TANK CIRCUIT TO MEET THE LOSES.
<3>FEED BACK CIRCUIT :- THE FEED BACK CIRCUIT SUPPLIES A
PART OF COLLECTOR ENERGY TO THE TANK CIRCUIT IN
CORRECT PHASE TO AID THE OSCILLATIONS i.e IT PROVIDES
POSITIVE FEED BACK.

63. DIFFERENT TYPES OF TRANSISTOR OSCILLATORS
A TRANSISTOR CAN WORK AS AN OSCILLATOR TO
PRODUCE CONTINOUS UNDAMPED OSCILLATIONS OF ANY
DESIRED FREQUENCY IF TANK AND FEED BACK CIRCUITS ARE
PROPERLY CONNECTED TO IT.ALL OSCILLATIONS UNDER
DIFFERENT NAMES HAVE SIMILAR FUNCTION i.e THEY
PRODUCE CONTINOUS UNDAMPED OUPUT.HOWEVER,THE
MAJOR DIFFERENCE THESE OSCILLATORS LIES IN THE
METHOD BY WHICH ENERGY IS SUPPLIED TO THE TANK
CIRCUIT TO MEET THE LOSSES.THE FOLLOWING ARE THE
TRANSISTOR OSCILLATORS COMMONLY USED AT VARIOUS
PLACES ELECTRONIC CIRCUITS :-
A. TUNED COLLECTOR OSCILLATOR
B. COLPITT’S OSCILLATOR
C. HARTLEY OSCILLATOR
D. PHASE SHIFT OSCILLATOR
E. WIEN BRIDGE OSCILLATOR
F. CRYSTAL OSCILLATOR

64. TWO BIT SIMULTANEOUS A/D CONVERTER
C3
REF VOLTAGE COMP
+3V/4
ANALOG
INPUT C2
VOLTAGE 0 REF VOLTAGE
TO V COMP
VOLTAGE +V/2
C1
REF VOLTAGE COMP
+V/4
LOGIC CIRCUITS
C3
+3V/4 COMP S Q 21
CODING READ
R Q
ANALOG
INPUT
C2 NETWORK GATES
DIGITAL
VOLTAGE +V/2 COMP
S Q OUTPUT
C1 20
R Q
+V/4

65. HALF SUBTRACTOR
D
INPUT OUTPUT
A
DIFFERENCE A B W D
HS 0 0 0 0
B W 0 1 1 1
BORROW 1 0 0 1
1 1 0 0
A
D
B DIFFERENCE
W
BORROW

66. 555 TIMER- MONOSTABLE
TRIGGER
a 1
0
TRIGGER
1
ã 0
a t t
LOGIC SYMBOL WAVE FORM
+5 to +15 V
+Vcc
RESET
4 8
TRIGGER
RA
NORMALLY 2
7
DISCHARGE
ON LOAD RL THRESHOLD
OUTPUT 6
3
NORMALLY 5 CONTROL
C
1 VOLTAGE
OFF LOAD RL

67. SYMBOLS AND TRUTH TABLES
D Q D E Q Q
X 0 QN QN
0 1 0 0
E Q
1 1 1 1
(a)
S R D CK Q Q
D S Q
1 1 1 1 0
CK 1 1 0 0 1
R Q 1 1 X QN
1 1 X 0 QN
(b) 1 1 X X 1 0
0 0 X X 0 1
J K S R CK Q Q
J S Q 0 1 QN QN
0 1
CK 0 1 1 1 0 1
1 0 1 1 1 0
K R Q 1 1 1 1 TOGGLE
(c) X X 1 1 0 QN QN
X X 1 1 1 QN QN
X X 0 1 X 1 0
X X 1 0 X 0
(a) D LATCH : WHEN E IS ENABLED THE INPUT DATA GETS LATCHED TO OUTPUT
(b) D FLIP FLOP : USED FOR REGISTERS.
(c) J K FLIP FLOP : USED FOR COUNTERS

68. BIT D/A CONVERTER
DIGITAL INPUT DATA
INPUT GATES
N BIT REGISTER
N LINES
LEVEL AMPLIFIERS
N LINES
RESISTIVE DIVIDER VA
DIGITAL INPUT
READ IN
2ō 20 2T 21 22 22 23 23 (STROBE PULSE)
S Q S Q S Q S Q
R Q R Q R Q R Q
PRECISION
VOLTAGE
SOURCE
LEVEL LEVEL LEVEL LEVEL
AMPLIFIER AMPLIFIER AMPLIFIER AMPLIFIER
R R R
2R 2R 2R 2R
2R
V

69. COMMON COLLECTOR AMPLIFIER
NPN
C 0.95 I
0.05 I B
VC
E
AC INPUT RL
I
+ - - +
VEE VCC
INPUT & OUTPUT SIGNALS ARE IN PHASE
LESS THAN 1
SUMMARY OF TRANSISTOR CIRCUIT, CHARACTERISTICS
INPUT OUTPUT CURRENT VOLTAGE POWER
IMPEDENCE IMPEDENCE GAIN GAIN GAIN
COMMON BASE 30-150 OHMS 300000- 1 LESS THAN 1 300-1000 20-30 DB
MEGAOHMS
COMMON 500-1500 OHMS 50000 OHMS 35 250-300 40 DB
EMITTER
COMMON 100000-500000 100-1000 35 LESS THAN 1 15-30 DB
COLLECTOR OHMS OHMS

70. DUALS
BASIC DUALITY UNDERLIES ALL BOLEAN ALGEBRA. EACH EXPRESSION
HAS ITS DUAL WHICH IS AS TRUE AS THE ORIGINAL EXPRESSION. FOR
GETTING THE DUAL OF GIVEN BOOLEAN EXPRESSION, THE PROCEDURE
IS TO CONVERT.
1. ALL 1s TO Os AND ALL Os TO 1s.
2. ALL ANDs TO ORs AND ALL ORs TO ANDs.
THE DUAL SO OBATINED IS A ALSO FOUND TO BE TRUE. SOME OF THE
BOOLEAN RELATIONS AND THEIR DUALS ARE GIVEN IN TABLE.
RELATION DUAL RELATION
A.O=0 A+1=1
A.A=1 A+A=A
A.A=0 A+A=1
A.1 =A A+0 =A
A. ( A + B ) = AB A + AB = 1
A + AB = A+B

71. PUSH PULL AMPLIFIER
DRIVER TR1 OUTPUT
TRANSFORMER TRANSFORMER
T1 T2
N1
N2
spk
TR2 Vcc
1
1
2 2

72. MICRO PROCESSOR
MICROPROCESSOR IS A SEMICONDUCTOR DEVICE MANU-
FACTURED BY USING LSI TECHNIQUE .IT INCLUDES THE ALU
CONTROL UNIT AND REGISTER ARRAY ON A SINGLE CHIP.
THE 8085 MICRO PROCESSOR
 IT IS A 8 BIT MP.
 POWER REQUIRES +5V & -5V.
 40 PIN DIP 1C.
 IT HAS 16 ADRESS LINES.
 IT HAS 8 DATA LINES.
 CLOCK FREQUENCY 5 MHZ
 DIFFERENT LEVEL OF INTERRUPTS ARE USED.
 MULTPEX ADRESS AND DATA BUS.

73. PINOUT DIAGRAM OF 8085 MP
X1 1 8 40 VCC
X2 2 0 39 HOLD
RESET OUT 3 8 38 HLDA
SOD 4 5 37 CLK<OUT>
SID 5 36 RESEST IN
TRAP 6 35 READY
RST 7.5 7 34 10/M
RST 6.5 8 33 5I
RST 5.5 9 32 RD
INTR 10 31 WR
INTA 11 30 ALE
ADO 12 29 50
AD1 13 28 A15
AD2 14 27 A14
AD3 15 26 A13
AD4 16 25 A12
AD5 17 24 A11
AD6 18 23 A10
AD7 19 22 A9
VSS 20 21 A8

74. DETAILS OF PINOUT DIAGRAM
OF
• 8085 MP
X1 RD - READ BAR/PIN
• X2 CRYSTAL FREQ WR - WRITE BAR/PIN
• 50D - SIGNAL OUT DATA SO - SIGNAL OUT
• 51D - SIGNAL IN DATA A15 to ADDRESS
• TRAP - INJ IN BETWEEN A8 BUS
• RST 7.5 TIMING FOR
• RST 6.5 INTERPT
• RST 5.5
• INTR - INTERPT
• INTA - INTERPT ADDRESS BAR
• AD0 ADDRESS BUS
• AD1 TO 16 BIT ADDRESS BUS
• AD &
• VCC - +5V SUPPLY VSS - -5V SUPPLY
• HOLD - TO HOLD COMMAND
• HLDA - HOLD ADDRESS
• CLK <OUT>
• 10/M - INPUT/OUTPUT MEMORY BAR
• SI - SIGNAL IN PIN

75. BLOCK DIAGRAM OF
COMPUTER
CENTRAL PROCESSING UNIT
(CPU )
CONTROL UNIT
INPUT MEMORY
OUTPUT
DEVICE DEVICE
ARITHMATIC&
LOGIC
UNIT

76. INPUT DEVICE OUTPUT DEVICE
1. PUNCH CARDS 1. VDU
2. PUNCHED 2. PRINTER
PAPERTAPE
3. MAGNETIC TAPE 3. PLOTTER
4. KEY BOARD OR 4. TYPE WRITER
TYPE WRITER 5. PUNCH CARDS
5. MAGNETIC DISK ETC.
6. OPTICAL
SCANNER
7. MAGNETIC INK
READER ETC.

77. CONTROL UNIT
1. INTERPRETS THE INSTRUCTIONS FED
INTO THE COMPUTER
2. DIRECTS & CONTROLS THE ACTIVITIES OF
THE INPUT DEVICES.(STORAGE
UNIT,ALU,& OUTPUT DEVICES NEEDED TO
EXECUT THE INST).
3. AUX. STORAGE IS ALSO UNDER THE
CONTROL OF THIS UNIT.