This document discusses timing and synchronization in digital communication systems. It explains that digital signals are transmitted as pulses or clocks, and receivers must detect these signals accurately by synchronizing to the transmitter's clock. Five methods of clock exchange are described to achieve synchronization between machines: free running, line-timed, loop-timed, external, and through-timed. Maintaining accurate synchronization is important to avoid errors that can reduce throughput or cause audible clicks in signals like voice and video.

1. Timing and Synchronization
Prepared by :
Mr. Muhammad Ahsan
Lecturer Computer Science, Preston University Peshawar
Pakistan.

2.  It is important to detect signals accurately at
the receiver side in terms of digital signals
0/1
 Digital signals transmits in the form of pulses
or clocks
 The ideal system is that in which the receiver
section knows exact the time the signal
brought in its self at the receiver interface

3.  This synchronization between between
transmitter and receiver is achieved because
each machine knows about each others
“clock”
 Clock : at which frequency on a specific time
sending machine sends its traffic to receiver
 The receiver can determine this time
because of pulses arrived at receiver end.

4.  An Error can be passed to the customer end
without having clock mechanism
 This error create problem and can be passed
among different nodes
 The error generated depend on thetraffic
being transmitted

5. Type of Traffic
 Digital Data
 Encrtpted Data
 Fax
 Video
 Voice
 Voice band Data
Result of Error
 Reduce throughput
 Resend Key
 Missing lines
 Picture freeze
 Audible click
 Carrier drop

6.  It carries information about time
 The signal is represented by a crossing mark
 To define clocking signals we use term unit
interval UI(corresponds to 1 cycle of clocking
signal)
 1 UI = 2 radian

7.  For achieving synchronization between the
machines we use different (5) methods of
clock exchange.
 1) Free Running
 2)Line-Timed
 3)Loop-Timed
 4)External
 5)Through Timed

8.  Each machine generates own timing(oscilator)
 Called free running/free running configuration
 No external clocking source is used
 Adv: no need to connect wid external timing source
 Dis/advn: DS3 incoming signals md outgoing buffuring

9.  Derives clocking on line from incoming signals
 Generator module fed these signals into local time nd provide timing to
outgoing signals
 Advn: simple
 Dis/advn: when several machines are connected where linearly to each
other

10.  Also called gateway or Master/Slave mode
 Used where different timing generators are deployed/ where
machins must intract with eachother
 Here the frequency sent from the running machine used to derive
clock at slave unit

11.  The slave unit may loop the clock back
across the line or may employ an externel
clock

12.  Machine times their transmitted signals from internel
oscillator that is locked with an externel
 Here synchronixation also known as plesiochronoius

13.  Last method of timing distribution
 Uses ring topology here
Building
Integrated
Timing Supply