Figure 8-4.--CCTV simplified block diagram.

The control amplifier combines the video, sync,

and blanking signals, all in proper sequence, into a

single continuous output to the amplitude modulator.

Circuits in the sync generator produce synchro-

nizing (sync) and blanking pulses. These pulses are

applied to the control amplifier and become a part of

the transmitted signal. Horizontal synchronization

makes the horizontal scanning at the receiver occur at

the same time as the horizontal scanning at the camera.

Vertical synchronization makes the vertical scanning

at the receiver keep in step with the vertical scanning

Figure 8-4.--CCTV simplified block diagram.

at the camera.

Sync and blanking signals are also fed to the

The camera tube provides a means of converting

camera circuits, which develop the necessary control

light, from an object on which the camera is focused,

signals for the electron gun and the sweep voltages for

into electrical impulses. Light from the object is

the deflection coils (both horizontal and vertical).

focused on the light-sensitive surface (called the

In the carrier, the principal circuit is an oscillator

mosaic or photoconductive material) in the camera

designed to produce a steady, continuous RF signal.

tube by the lens system. The camera tube contains an

Its frequency is fixed and designated by appropriate

electron gun, which generates and controls a stream of

civil authority for the TV station in which it is used.

electrons. The gun directs the narrow stream of

In the amplitude modulator, the carrier signal is

electrons in such a manner that it traverses (scans) the

modulated by the video, sync, and blanking pulses.

mosaic line by line. As the beam strikes a spot in the

The composite (total) signal is then amplified by the

mosaic, it generates a small electrical impulse that

R amplifier and fed to the antenna for radiation into

corresponds to the lightness or darkness of that

space.

particular tiny portion of the image. The electrical

impulses generated in this manner are sent to the video

The sound portion of the television signal is

amplifier (fig. 8-3).

transmitted by a frequency modulated R carrier. The

sounds are picked up by a microphone, amplified by

Control Unit

the audio amplifier, and fed to the frequency

modulator section. The sound earner frequency is

The control unit, as the name implies, is the

varied according to the frequency of the audio signal

being picked up by the microphone. The frequency

heart of the system. This unit connects all the other

modulated signal is then amplified by an R power

units of the system together. Drive pulses are

amplifier. Then it is fed to the antenna for radiation

generated, and they develop the sweep and blanking

into space, or into a cable system installed throughout

signals required by the camera. Synchronizing and

the ship.

blanking pulses are supplied by the control unit to

the receiver/monitor.

Receiver/Monitor

Video signals from the camera are amplified and

distributed to the receiver/monitor. The output signals

The picture-producing unit is commonly referred

from the control unit contain vertical and horizontal

to as the receiver/monitor unit. The receiver and the

blanking, sync, and video signals. The control unit

monitor (fig. 8-4) differ basically only in the circuits

consists of the following sections, shown in figure 8-3:

contained in each unit. The media of transmission

video amplifier, control amplifier, carrier, amplitude

between the receiver and monitor units are different.

modulator, radio-frequency (RF) amplifier, sync

This difference requires the receiver to employ

generator, and the audio controls.

additional circuits. (The media employed for the

Video amplifiers are designed to amplify a wide

receiver is radio waves, while the media for the

range of frequencies. The weak electrical impulses

monitor is normally cables.) The standard TV receiver

from the camera tube are built up by the video

contains the same circuits as the monitor, and, in

amplifier and fed to a control amplifier.

addition, contains the antenna system, tuner, R

8-7