# Data Transmission

DATA TRANSMISSION:

The electronic transfer of data from a transmitter to receiver. It’s of two types.

v      Guided Transmission. / Direct Link / Point to Point : the transmission path b/w 2 devices in which signals propagate directly from transmitter to receiver with no intermediate devices (except amplifier & repeater etc to increase the strength ) e,g cable media, twisted pair, optical fiber

v      Un Guided transmission / In Direct Link / Multipoint : more than 2 devices share the link. e.g. air, water,   vacuum

TRANSMISSION MODES:

v      Simplex: signals r transmitted only n one direction. One transmitter & one receiver. e.g tv sys, cable, radio

v      Half duplex: Either direction, but only one way at a time. e.g. police radio, chatting, wireless.

v      Full duplex: Both directions at the same time. e.g. telephone, RADAR.

SIGNALS:

Electric or electromagnetic representations of data.

v      Analog / Continuous Signals: in which the signal intensity varies in a smooth way over time.

v      Digital / Discrete Signals: Maintains a constant level for some period of time then changes to another constant level…..

X-axis of signals s always t or theta.

F of dig signal s always 0.

TIME DOMAIN: when the X-axis is t

FREQUENCY DOMAIN: when X-axis is f

PERIODIC SIGNALS:

A signal which repeat itself after equal intervals of time & maintains its periodicity is called a periodic signal. Digital signals, radars signals are periodic but signals on telephone are not periodic.

S ( t + T ) = S ( t )à T=Time period , t=any time, S=signals.

S ( 0 + 2min ) = S ( 0 )

S ( 30 + 2min ) = S ( 30 )

Periodic signal is known as Sinusoidal signal. It has sin & cos both

Rad = / 180 * angle

PARAMETERS OF SINOSIDAL WAVES:

AMPLITUDE:

Max height which a signal can achieve above the reference axis, denoted by A measured in distance unit  (m, cm) .

TIME PERIOD:

Total time taken to complete one full cycle denoted by T measured in time unit (s, min)

FREQUENCY:

Num of cycles per unit time denoted by f =1/T, measured in HZ.

WAVELENGTH:

Distance b/w two consecutive crests or two consecutive trough is cal     measured in distance length

PEAK TO PEAK VALUE:

Distance b/w max point (peak) & min point (peak) denoted by p-p measured in distance unit.

CO-AXIAL CABLE: