consequent distortion. Many circui ry
names—clipping, blocking, slicing, li ave,
etc.—show that they are designed to r than
to preserve them. Finally, he would d contours
manipulated with a split-microse own in his
time. The most important practical techniques
is radar. We usually think of radar nd bombing or
obstacle detection. Basically radar me measurement
of exquisite precision, and wh he scope is only a
derivative of what we measure onds. We send out
square-shaped pulses, usually of econd duration, pick up
the reflection from a target, mea lapsed time electronically
and automatically, convert it in nce, dis-play the result on a
tube, and that’s radar.
Used in Navigation Aids
Another application of microsecond technique is the Loran
navigation system (PS, Feb. ‘48, p. 78). Like radar, it uses
rectangular pulses, but they are transmitted on a comparatively long
wave length from a number of widely separated locations. Thus they
cover a much greater range than radar, which, like television, is
limited to the optical horizon. The method is to measure the time of
transmission from each transmitter and thus to obtain a fix by
triangulation. The individual pulses are relatively long—about 40
microseconds—but it is a split-microsecond technique, for the
transmitters are synchronized to within 0.5 microsecond.
Another field for pulse-transmitting devices lies in guided-missile
control. The problem here is to feed data to a built-in radio receiver,
which will guide the missile to a target. Continuous waves may be
used for this purpose, but pulse control offers the advantage of
coding, so that the receiver will respond only to friendly emissions
and the enemy will be unable to take over control of the missile forPOPSCI.COM.AU 75