This document provides guidance for engineering technicians on interpreting engineering drawings for electronic, electrical, and communication circuits. It begins with an overview of the steps to interpret engineering information, which are to identify components, understand their purpose, and determine the overall circuit purpose. It then details the standard symbols and functions of common circuit components for electronic circuits like wires, power supplies, switches and resistors. The same is done for electrical circuits covering logic gates. Finally, communication circuit components are explained including routers, switches, hubs and network diagrams. Activities are included to have technicians interpret sample circuit diagrams.

1. Communications For
Engineering
Technicians
Week No. 1& 2

2. Contents
• How to interpret as an engineer the
following :
1. Electronic Circuits.
2. Electrical Circuits.
3. Communication Circuits
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3. How can we interpret the engineering
drawings in the electrical department?
 In our department we need to know the steps that let us able to
interpret the engineering information.
 So in this session we will produce to you the steps that we and
you will follow in interpreting the engineering information which
are:
1. You need to determine the electrical/Electronic/communication
components.
2. Then know the its main purpose of these components in these
circuits.
3. Then after you collect these information, we will know the
purpose of these circuits.
 Note that we will implement these steps in the following types of
circuits:
1- Electronic circuits.
2- Electrical circuits.
3- Communication circuits.
Prepared By Communication Team

4. 1- Electronic Circuits:
 At first we need to review in all the electronic components that we
studied in the previous years, So in this session we will produce to
you the steps that we and you will follow in interpreting the
engineering information which are:
Wires and connections- 1
Component
Circuit Symbol
Function of Component
Wire
To pass current very easily from one part of a
.circuit to another
Wires joined
A 'blob' should be drawn where wires are
connected (joined), but it is sometimes omitted.
Wires connected at 'crossroads' should be
staggered slightly to form two T-junctions, as
shown on the right.
Wires not joined
In complex diagrams it is often necessary to
draw wires crossing even though they are not
connected. I prefer the 'bridge' symbol shown
on the right because the simple crossing on the
left may be misread as a join where you have
forgotten to add a 'blob'!
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5. Power Supplies- 2
Component
Circuit Symbol
Function of Component
Cell
Supplies electrical energy.
The larger terminal (on the left) is positive (+).
A single cell is often called a battery, but strictly a
battery is two or more cells joined together.
Battery
Supplies electrical energy. A battery is more than
one cell.
The larger terminal (on the left) is positive (+).
DC supply
Supplies electrical energy.
DC = Direct Current, always flowing in one
direction.
AC supply
Supplies electrical energy.
AC = Alternating Current, continually changing
direction.
Fuse
circuit breaker
A safety device which will 'blow' (melt) if the
current flowing through it exceeds a specified
value.
a device that automatically breaks an electrical
circuit whenever the circuit becomes overloaded or
an unintentional short circuit occurs
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6. Power Supplies- 2
Component
Circuit Symbol
Function of Component
Transformer
Two coils of wire linked by an iron core.
Transformers are used to step up (increase) and
step down (decrease) AC voltages. Energy is
transferred between the coils by the magnetic field
in the core. There is no electrical connection
between the coils.
Earth
(Ground)
A connection to earth. For many electronic circuits
this is the 0V (zero volts) of the power supply, but
for mains electricity and some radio circuits it
really means the earth. It is also known as ground.
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7. Switches- 3
Component
Circuit Symbol
Function of Component
Push Switch
(push-to-make)
A push switch allows current to flow only when the
button is pressed. This is the switch used to operate a
doorbell.
Push-to-Break Switch
This type of push switch is normally closed (on), it is
open (off) only when the button is pressed.
On-Off Switch
(SPST)
SPST = Single Pole, Single Throw.
An on-off switch allows current to flow only when it
is in the closed (on) position.
2-way Switch
(SPDT)
SPDT = Single Pole, Double Throw.
A 2-way changeover switch directs the flow of current
to one of two routes according to its position. Some
SPDT switches have a central off position and are
described as 'on-off-on'.
Dual On-Off Switch
(DPST)
DPST = Double Pole, Single Throw.
A dual on-off switch which is often used to switch
mains electricity because it can isolate both the live
and neutral connections.
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8. Switches- 3
Component
Reversing Switch
(DPDT)
Relay
Circuit Symbol
Function of Component
DPDT = Double Pole, Double Throw.
This switch can be wired up as a
reversing switch for a motor. Some
DPDT switches have a central off
position.
An electrically operated switch, for
example a 9V battery circuit
connected to the coil can switch a
230V AC mains circuit.
NO = Normally Open,
COM = Common, NC = Normally
Closed.
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9. 4- Resistors
Component
Resistor
Circuit Symbol
Function of Component
A resistor restricts the flow of current, for example
to limit the current passing through an LED. A
resistor is used with a capacitor in a timing circuit.
Some publications still use the old resistor symbol:
Variable Resistor
(Rheostat)
This type of variable resistor with 2 contacts (a
rheostat) is usually used to control current.
Examples include: adjusting lamp brightness,
adjusting motor speed, and adjusting the rate of
flow of charge into a capacitor in a timing circuit.
Variable Resistor
(Potentiometer)
This type of variable resistor with 3 contacts (a
potentiometer) is usually used to control voltage. It
can be used like this as a transducer converting
position (angle of the control spindle) to an
electrical signal.
Variable Resistor
(Preset)
This type of variable resistor (a preset) is operated
with a small screwdriver or similar tool. It is
designed to be set when the circuit is made and
then left without further adjustment. Presets are
cheaper than normal variable resistors so they are
often used in projects to reduce the cost.
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10. 5- Capacitors
Component
Circuit Symbol
Function of Component
Capacitor
A capacitor stores electric charge. A capacitor is
used with a resistor in a timing circuit. It can also
be used as a filter, to block DC signals but pass AC
signals.
Capacitor, polarised
A capacitor stores electric charge. This type must
be connected the correct way round. A capacitor is
used with a resistor in a timing circuit. It can also
be used as a filter, to block DC signals but pass AC
signals.
Variable Capacitor
A variable capacitor is used in a radio tuner.
Trimmer Capacitor
This type of variable capacitor (a trimmer) is
operated with a small screwdriver or similar tool.
It is designed to be set when the circuit is made
and then left without further adjustment.
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11. 6- Diodes
Component
Circuit Symbol
Function of Component
A device which only allows current to flow in one
Diode
direction.
LED
Light Emitting Diode
A transducer which converts electrical energy to
light.
A special diode which is used to maintain a fixed
Zener Diode
voltage across its terminals.
Photodiode
A light-sensitive diode.
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12. 7- Transistors
Component
Circuit Symbol
Function of Component
A transistor amplifies current. It can be used with
Transistor NPN
other components to make an amplifier or
switching circuit.
A transistor amplifies current. It can be used with
Transistor PNP
other components to make an amplifier or
switching circuit.
Phototransistor
A light-sensitive transistor.
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13. Activity No.1
 USE YOUR TECHNICAL INFORMATION ABOUT CIRCUIT/NETWORK
DIAGRAM TO INTERPRET THESE CIRCUITS:
Circuit No.1
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14. Circuit No.2
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15. Circuit No.3
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16. Circuit No.4
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17. 2- Electrical Circuits:
 At first we need to review in all the electrical components that we
studied in the previous years, So in this session we will produce to
you the steps that we and you will follow in interpreting the
engineering information which are:
: Logic Gates- 1
).Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off
Component
NOT
AND
Circuit Symbol
Function of Component
A NOT gate can only have one input. The
'o' on the output means 'not'. The output of
a NOT gate is the inverse (opposite) of its
input, so the output is true when the input is
false. A NOT gate is also called an inverter.
An AND gate can have two or more inputs.
The output of an AND gate is true when all
its inputs are true.
Prepared By Communication Team

18. : Logic Gates- 1
).Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off
Component
NAND
Circuit Symbol
Function of Component
A NAND gate can have two or more inputs.
The 'o' on the output means 'not' showing
that it is a Not AND gate. The output of a
NAND gate is true unless all its inputs are
true.
OR
An OR gate can have two or more inputs. The
output of an OR gate is true when at least one
of its inputs is true.
NOR
A NOR gate can have two or more inputs.
The 'o' on the output means 'not' showing
that it is a Not OR gate. The output of a NOR
gate is true when none of its inputs are true.
Prepared By Communication Team

19. : Logic Gates- 1
).Logic gates process signals which represent true (1, high, +Vs, on) or false (0, low, 0V, off
Component
Circuit Symbol
Function of Component
An EX-OR gate can only have two inputs.
XOR
The output of an EX-OR gate is true when its
inputs are different (one true, one false).
An EX-NOR gate can only have two inputs.
The 'o' on the output means 'not' showing
XNOR
that it is a Not EX-OR gate. The output of an
EX-NOR gate is true when its inputs are the
same (both true or both false).
Prepared By Communication Team

20. Activity No.2
 USE YOUR TECHNICAL INFORMATION ABOUT CIRCUIT/NETWORK
DIAGRAM TO INTERPRET THESE CIRCUITS:
Circuit No.1
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21. Circuit No.2
A
B
Y
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HOSSAM hedait

22. Circuit No.3
A
Y
B
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23. 3- Communication Circuits:
 At first we need to review in all the communication components
that we studied in the previous years, So in this session we will
produce to you the steps that we and you will follow in interpreting
the engineering information which are:
1- Communication Components:
Component
Circuit Symbol
Function of Component
Router
A Router is an internetworking device which
operates at OSI Layer 3. A Router
interconnects network segments or entire networks
and passes data packets between
networks based on Layer 3 information. The
router, by default, is an open device.
Services must be turned off or secured.
Switch
Switches connect LAN segments, use a table of
MAC addresses to determine the
segment on which a datagram needs to be
transmitted, and reduce traffic. Switches,
which typically operate at Layer 2, can be
categorized as stackable or chassis based.
Prepared By Communication Team

24. 1- Communication Components:
Component
Circuit Symbol
Function of Component
Hub
Hubs, or multiport repeaters, are legacy devices
which combine connectivity with the
amplifying and re-timing properties of repeaters.
Hubs operate at Layer one of the OSI.
It is typical to see 4, 8, 12, and up to 24, ports on
multiport repeaters. This allows many
devices to be cheaply and easily interconnected.
Server
In most networks, servers are the brains of the
operation while networking devices
provides the nervous system of the business. It is
very important that these resources
are protected against attacks.
Corporate
Headquarter
The Corporate Headquarter (HQ) is where the
primary network resides. The HQ is a
central point of connection between branch offices,
business partners, remote users, and
the Internet. Devices located at the HQ are most
critical to protect.
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25. 1- Communication Components:
Component
Circuit Symbol
Function of Component
Personal
Computer
The Personal Computer (PC) has only been
around for 25 years and has greatly
changed the world. Functionality, performance,
and storage have greatly increased. With
the advent of the Internet, PCs have become
commonplace in governments, businesses,
schools, and homes. Unfortunately, with increased
capabilities and connectivity, security
vulnerabilities in applications and operating
systems are a big problem. It is these
vulnerabilities, which are exploited by hackers
today. With broadband services such as
DSL and Cable, the attacks have increased
dramatically.
Network Cloud
The Network Cloud represents a wide area
network (WAN) or the Internet. Network traffic
can traverse private and public links depending on
the established service and
connections. Also, data can traverse a single
Internet service provider (ISP) or multiple
ISPs.
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26. 1- Communication Components:
Component
Modem
IOS Firewall
Firewall
Circuit Symbol
Function of Component
A modem is a device which provides connectivity
to the ISPs network access server. A modem can
terminate dial-up connections, xDSL, or Cable
connections.
The Cisco IOS Firewall, provides robust,
integrated firewall, intrusion detection, and VPN
functionality for every perimeter of the network.
The Firewall Feature Set is available for most
Cisco routers including the 800, 1600, 1700, 2500,
2600, 3600, 7100, and 7200 series routers, however
some features may not be available on low end and
legacy router models.
Firewall provides large enterprises and service
providers with unmatched security, reliability, and
performance within a switch chassis.
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27. 1- Communication Components:
Component
Ethernet Link
Circuit Symbol
Function of Component
Ethernet Links provide connectivity for the entire
network. These links interconnect routers,
switches, printers, PCs, laptops, servers, and other
end devices. Current Ethernet links operate at
from 10Mbps to 10Gbps. Ethernet can run over
fiber and copper.
Wan Link
WAN Links provide connectivity to the Internet.
WAN technologies can be classified as packet
switched, circuit switched or cell switched.
Technologies include dial-up, ISDN, X.25, xDSL,
Satellite, Cellular, Cable, Frame Relay, SMDS,
ATM, SONET. Speeds range from 28Kbps to
10Gbps.
Attacker
Attackers access the network either internally or
externally. Remember that 75 percent of
the attacks come from within the network.
Attackers can be curious users, corporate
spies, government operatives, careless users,
disgruntled employees, or elite hackers.
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28. Activity No.3
 USE YOUR TECHNICAL INFORMATION ABOUT CIRCUIT/NETWORK
DIAGRAM TO INTERPRET THESE CIRCUITS:
Circuit No.1
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29. Circuit No.2
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30. Circuit No.3
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31. Activity No.4
IDENTIFY THE STANDARD
SYMBOLS AND CONVENTIONS YOU
HAVE USED BY ADDING BRIEF
NOTES TO THE HARD COPY OF
YOUR ACTIVITIES.
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32. THANK YOU FOR LISTENING
Questions
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