A complete ppt for network connectors and interface standards. Modems with types and version are also added in it. utility of cable modem alongwith null modem are described in it. a useful presentation for persons looking for networking devices at physical layer.

1. Data Communication & Networking
Physical Layer-
Interface, Standards, Connectors
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2. Connecting Devices
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3. Electronic Industries Association (EIA) Standard
/RS-232
• RS-232 is a standard for serial communication
transmission of data.
• It formally defines the signals connecting
between a DTE (data terminal equipment) such
as a computer terminal, and a DCE (data circuit-
terminating equipment or data communication
equipment), such as a modem
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4. EIA 232-D Interface Specification
1. Mechanical specifications:-gives details of the mechanical dimensions
and the type of connectors to be used on the device & the medium. Pin
assignment of the connector are also specified.
2. Electrical specifications:-defines the permissible limits of the electrical
signal appearing at the interface in terms of voltage, current, impedance,
rise time etc. The required electrical characteristics of the medium are
also specified.
3. Functional specifications:- indicates the functions of various control
signals
4. Procedural specifications:- indicates the sequence in which the control
signals are exchanged between the physical layer for carrying out their
functions.
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5. EIA 232 interface is applicable to the following
modes of transmission:
1. Serial transmission of data
2. Synchronous and asynchronous transmission
3. Point-to-point and point-to-multipoint working
4. Half duplex and full duplex transmission
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6. EIA 232/RS 232
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8. EIA 449/ RS-449
• RS-449 mechanical specifications defines a combination of two connectors that uses a
DB-37 connector and a DB-9 for combined 46pins.
• Its functional specifications gives the data-37 pins properties similar to those of DB-25.
• The major functional difference between the 25 & 37 pin connectors is that all functions
relating to the secondary channel have been removed from DB-37.
• To maintain compatibility with EIA-232,EIA-449 defines two category of pins to be
used in exchanging data, control & timing information.
1. Category I Pins :-includes those pins whose functions are compatible with
RS232,though most have been removed.
2. Category II Pins :- those that have been redefined and no equivalence with EIA-
232.
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9. EIA-449 DB’s
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10. EIA-449 DB’s
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11. Pin Signal Name Description Pin Signal Name Description
1 Shield 19 SG Signal Ground
2 SI Signal Rate Indicator 20 RC Receive Common
3 n/a unused 21 n/a unused
4 SD- Send Data (A) 22 SD+ Send Data (B)
5 ST- Send Timing (A) 23 ST+ Send Timing (B)
6 RD- Receive Data (A) 24 RD+ Receive Data (B)
7 RS- Request To Send (A) 25 RS+ Request To Send (B)
8 RT- Receive Timing (A) 26 RT+ Receive Timing (B)
9 CS- Clear To Send (A) 27 CS+ Clear To Send (B)
10 LL Local Loopback 28 IS Terminal In Service
11 DM- Data Mode (A) 29 DM+ Data Mode (B)
12 TR- Terminal Ready (A) 30 TR+ Terminal Ready (B)
13 RR- Receiver Ready (A) 31 RR+ Receiver Ready (B)
14 RL Remote Loopback 32 SS Select Standby
15 IC Incoming Call 33 SQ Signal Quality
16 SF/SR+
Signal Freq./Sig. Rate
Select.
34 NS New Signal
17 TT- Terminal Timing (A) 35 TT+ Terminal Timing (B)
18 TM- Test Mode (A) 36 SB Standby Indicator
37 SC Send Common
DB-37 Pin Description
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12. DB-37
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13. DB-9 Pin Description
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Pin Signal Name Description
1 Shield
2 SRR Secondary Receive Ready
3 SSD Secondary Send Data
4 SRD Secondary Receive Data
5
SG Signal Ground
6
RC Receive Common
7 SRS Secondary Request to Send
8 SCS Secondary Clear to Send
9 SC Send Common

14. DB-9
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15. Standard telephone cable connectors, RJ-11 has 4 wires (and RJ-
12 has 6 wires). RJ-11 is the acronym for Registered Jack-11, a
four- or six-wire connector primarily used to connect telephone
equipment.
RJ-11 Pin Signal Name
1 VCC (5 volts regulated)
2 Power Ground
3 One Wire Data
4 One Wire Ground
RJ-11 (Registered Jack)
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RJ11 Connector

16. RJ11 Connector for RS 232 Communication
RJ11 Connector
Pin Signal Description I/O
1 NC --
2 +5V +5V power only for STU, left it unconnected when
connect to a PC serial port /NC
O
3 TxD RS232 transmit. O
4 GND Ground. GND
5 RxD RS232 receive. I
6 NC --
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17. The acronym for Registered Jack-45 is RJ-45. The RJ-45 connector is
an eight-wire connector that is commonly used to connect computers to
a local area network (LAN), particularly Ethernet LANs. Although they
are slightly larger than the more commonly used RJ-11 connectors, RJ-
45s can be used to connect some types of telephone equipment.
RJ45 Connector
RJ-45 (Registered Jack)
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18. Difference Between RJ45 and RJ11
• The main difference between these two is in where they are actually used.
RJ45 jacks are used in networking, where you connect computers or other
network elements to each other. RJ11 is the cable connector that is being
used in telephone sets.
• The number of cables that are accommodated in each connector. here are
only four wires inside and RJ11 while there are eight wires inside an RJ45.
As a consequence of having to accommodate more wires, RJ45 connectors
are also a little bit bigger than RJ11s.
Summary
1.RJ45 is used with ethernet cables in computer networking
while RJ11 is used in connecting telephone units
2.RJ45 contains more wires than RJ11
3.RJ45 is physically bigger than RJ11 to accommodate the
extra wires
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19. BNC Connectors
• The BNC (Bayonet Neill–Concelman)
connector is a miniature quick
connect/disconnect radio frequency used for
coaxial cable.
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20. BNC Tee connectors
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21. Applications
1. Originally designed for military use
2. Has gained wide acceptance in video and RF applications to
2 GHz.
3. The BNC connector is used for signal connections such as:
i. analog and serial digital interface video signals
ii. amateur radio antennas
iii. aerospace electronics (avionics)
iv. test equipment.
4. Used for composite video on commercial video devices.
5. Commonly used on 10base2 thin Ethernet network cables
and network cards.
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22. Aspects to digital-to Analog conversion
• Bit Rate / Baud Rate
– Bit rate is the number of bits per second. Baud rate is the number
of signal units per second. Baud rate is less than or equal to the bit
rate.
– Bit rate is important in computer efficiency
– Baud rate is important in data transmission.
• Baud rate determines the bandwidth required to send signal
– Baud rate = bit rate / # bits per signal unit
– An analog signal carries 4 bits in each signal unit. If 1000 signal
units are sent per second, find the baud rate and the bit rate
• Baud rate = 1000 bauds per second (baud/s) Bit rate = 1000 x 4
= 4000 bps
– The bit rate of a signal is 3000. If each signal unit carries 6 bits,
what is the baud rate?
• Baud rate = 3000/6 =500 bauds/secPrepared By: Srashti Vyas

23. MODEM
• A modem (modulator-demodulator) is a network hardware device that
modulates one or more carrier wave signals to encode digital information for
transmission and demodulates signals to decode the transmitted information.
• The goal is to produce a signal that can be transmitted easily and decoded to
reproduce the original digital data.
• A common type of modem is one that turns the digital data of a computer into
modulated electrical signal for transmission over telephone lines and
demodulated by another modem at the receiver side to recover the digital data.
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24. Classification of MODEM/ MODEM Standards
• Classified by the amount of data they can send in a given
unit of time, usually expressed in bits per second (symbol
bit/s, sometimes abbreviated "bps"), or bytes per second
(symbol B/s).
• Classified by their symbol rate, measured in baud. The
baud unit denotes symbols per second, or the number of
times per second the modem sends a new signal.
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Bit Baud comparison
Modulation Units
Bits/Ba
ud
Baud
rate
Bit
Rate
ASK, FSK, 2-PSK Bit 1 N N
4-PSK, 4-QAM Dibit 2 N 2N
8-PSK, 8-QAM Tribit 3 N 3N
16-QAM Quadbit 4 N 4N
32-QAM Pentabit 5 N 5N
64-QAM Hexabit 6 N 6N
128-QAM Septabit 7 N 7N
256-QAM Octabit 8 N 8N

26. Phone modems
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27. Classification of MODEM/ MODEM Standards
Today most of the modems are V-series standards published by the ITU-T.
1. V.32:Uses a combined modulation and encoding technique called Trellis-coded
modulation.
2. V.32bis: First of the ITU-T standards to support 14400 bps transmission. Uses 128 QAM
transmission at a rate of 2400 baud. An additional feature provided by V.32bis, is inclusion
of an automatic fall-back and fall forward feature that enables the modem to adjust its
speed upward or downward depending on the quality of the line or signal.
3. V.34bis:Provides a bit rate of 28,800 with a 960-point constellation and a bit rate of 33,600
bps with a 1664-point constellation.
4. V.90: These modem with a bit rate of 56kbps are available, these are called 56K modems.
These modem may be used only if one party is using digital signaling(such as through an
internet provider).
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28. V-series (ITU-T Standards)
• V-32.
– Uses a combined modulation and encoding technique: Trellis coded
Modulation.
– Trellis = QAM + a redundant bit
– 5 bit (pentabit) = 4 data + 1 calculated from data.
– A signal distorted by noise can arrive closer to an adjacent point than the
intended point (extra bit is therefore used to adjust)
– Less likely to be misread than a QAM signal.
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2400 baud • 4 bit = 9600 bps

29. V-series (cont.)
• V-32.bis
– First ITU-T standard to support 14,400 bps transmission.
– Uses 128-QAM
• (7 bits/baud with 1 bit for error control)
• at a rate 2400 baud 2400 * 6 = 14,400 bps
– Adjustment of the speed upward or downward depending on the quality of
the line or signal
• V-34 bis
– Bit rate of 28,800 bps with 960-point constellation to 1664-point
constellation for a bit rate of 33,600 bps.
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30. Constellation Diagram
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Constellation diagram for V.32 Constellation diagram for V.32bis

31. V-series (cont.)
• V-90
– Traditionally modems have a
limitation on data rate (max.
33.6 Kbps)
– V-90 modems can be used (up to
56Kbps) if using digital
signaling.
• For example, Through an
Internet Service Provider
(ISP)
– V-90 are asymmetric
• Downloading rate (from ISP
to PC) has a 56 Kbps
limitation.
• Uploading rate (from PC to
IST) has a 33.6 Kbps
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32. V-90/92 (cont.)
• V-90
– In uploading, signal still to be
sampled at the switching station.
Limit due to noise sampling.
– Phone company samples at 8000
times/sec with 8 bits (including
bit error)
• Data rate = 8000 * 7 =
56Kbps
– In download, signal is not
affected by sampling.
• V-92
– Speed adjustment
– Upload data at 48Kbps.
– Call waiting service
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33. Cable Modem
• A cable modem is a device that enables you to hook up your PC to
a local cable TV line and receive data at about 1.5 Mbps.
• A cable modem can be added to or integrated with a set-top box
that provides your TV set with channels for Internet access. In
most cases, cable modems are furnished as part of the cable access
service and are not purchased directly and installed by the
subscriber.
• A cable modem has two connections: one to the cable wall outlet
and the other to a PC or to a set-top box for a TV set.
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Motorola SURFboard SBV6120E
EuroDOCSIS 3.0 cable modem

34. TYPES OF MODEM
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Connection Modulation Bit rate(Kbps)
110 baud Bell 101 modem FSK 0.1
300 baud (Bell 103 or V.21) FSK 0.3
1200 modem (1200 baud) (Bell 202) FSK 1.2
2400 modem (600 baud) (V.22bis) QAM 2.4
2400 modem (1200 baud) (V.26bis) PSK 2.4
4800 modem (1600 baud) (V.27ter) PSK 4.8
9600 modem (2400 baud) (V.32) QAM 9.6
14.4k modem (2400 baud) (V.32bis) trellis 14.4
19.2k modem (2400 baud) (V.32terbo) trellis 19.2
28.8k modem (3200 baud) (V.34) trellis 28.8
33.6k modem (3429 baud) (V.34) trellis 33.6
56k modem (8000/3429 baud) (V.90) digital 56.0/33.6
56k modem (8000/8000 baud) (V.92) digital 56.0/48.0

35. NULL MODEM
• When we need to connect two DTE, in same building or when a terminal &
the host computers in vicinity(less than 15m apart), we don’t use MODEM.
• We need an interface to handle the exchange or an intermediary device which
has DCE ports on both sides that face DTE’s. This device is called “Null
Modem”, because it may not contain any electronic device or modem.
• A Null Modem provides the DTE-DTE interface without the DCE’s.
• Null modem is a communication method to directly connect two DTEs
(computer, terminal, printer, etc.) using an RS-232 serial cable.
• With a null modem connection the transmit and receive lines are cross linked.
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36. • The null modem cable is frequently called a crossover cable.
• For this to happen, the Transmit (TXD) pin of one device needs to be
connected to the Receive (RXD) pin of the other device.
• To enable handshaking between the two devices, the Request to Send
(RTS) pin of one device must be connected to the Clear to Send (CTS) pin
of the other device. Because these pins are "crossed" on the two cable
terminals, the name crossover cable is used.
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37. Prepared By: Srashti Vyas
Simple Null Modem Cable
Null Modem Cable with Handshaking

38. Null Modem
• Direct connection between two DTEs, e.g., terminal
and computer, or two computers directly
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DTE
DSR
DTR
CTS
RTS
RCV
XMIT
GND
Shield
DTE
DSR
DTR
CTS
RTS
RCV
XMIT
GND
Shield

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