Dan'1 Rex, age 10, of Allentown, Pa., for his question:

HOW DOES A TELEVISION CAMERA WORK?

We wonder today how we could live without television, and how we ever managed without it just a few years ago. It has certainly become an important part of our lives.
Television is a system of electronically reproduced visual images. It's a lot like motion pictures except that with TV electronic tubes replace the photographic film that is used in the movies.
Television, very simply, works its wonders in three principal steps: a picture is recorded with a TV camera; the image is transmitted on radio waves or special cables, and the receiver converts the electronic image to a picture for viewing. Sound is normally transmitted as radio waves with the image.
TV cameras are made up of a lens system, a camera tube and many electronic circuits. The lens system focuses the light rays of the scene being recorded on the face of the camera tube.
An (ital) image orthicon (unital) tube is a widely used camera tube that has an_extremely high sensitivity and is adaptable to changing light conditions. It has three main parts: a screen, a target and an electron gun.
When the scene is focused upon the light sensitive screen photoelectrons are emitted and flow toward the target. When the photoelectrons hit the target, additional electrons are knocked off the target, leaving it with a positive charge at that point.
Bright light focused from white objects produces a heavy fiow of electrons to the target, while weaker light focused from the dark areas produces.a weak flow of electrons. The target forms an electronic image or the recorded scene. The entire target image cannot be transmitted all at one time.
The electron gun is a device which scans tiny sections of the target rapidly, sending strong or weak electronic impulses to the transmitter depending upon the strength of the charge on the target. A beam of electrons emitted from the gun moves from the ieft to right across the target. At the end of each sweep, the beam returns to the left but moves a fraction of an inch lower.
The process is repeated until the entire picture is scanned.
Two separate scans are made to cover the whole image. The odd numbered horizontal lines (one, three, five and so on) are swept first, tollowed by the even numbered lines.
The Federal Communications Commission requires that images be scanned with 525 lines at the rate of 30 pictures per second. The scanning beam, therefore, moves horizontally in less than one 15,OOOth of~a second, completing the odd line scan in one 60th of a second.