According to the text, what did the disaster at Pearl Harbor show that the U.S. military leaders needed?
a way to improve the speed of the telegraph code
a secure system for communication with their troops
a way to prepare military bases' defenses more quickly
a secure system for recording and playing music
In this text, the author describes a sequence of technological developments.
In what order were these technologies created?
the Vocoder, SIGSALY, CDs, MP3 music files
MP3 music files, SIGSALY, CDs, the Vocoder
CDs, MP3 music files, the Vocoder, SIGSALY
SIGSALY, the Vocoder, CDs, MP3 music files
The method used by SIGSALY to encode messages was more effective than the method used by the Scrambler to encode messages.
What evidence from the text best supports this conclusion?
More than 3,000 high-level conversations happened over SIGSALY, covering troop movements, equipment drops, and military strategy.
Marshall didn't trust the Scrambler for his secure military communications, so he decided to send his message to Hawaii via telegraph code.
The SIGSALY system saw the first transmission of speech using pulse-code modulation and the first effective use of bandwidth compression to recreate speech.
The Germans were able to crack the code for the Scrambler, while no record has ever been found of the German or Japanese militaries decoding SIGSALY's messages.
Which machine had the most direct impact on the way music is recorded and played?
What is the main idea of the text?
SIGSALY was the first digital voice encoding system, and it used a process called pulse-code modulation to encode human speech.
Thousands of people were killed at Pearl Harbor due to the failure of the U.S. military's secure communications system.
A voice encoding system made for military use was the basis for some of today's digital music systems.
While CDs and MP3s both used pulse-code modulation to record and play music, they have very different physical forms.
Read these sentences about the Vocoder, a voice encoding machine.
The disaster at Pearl Harbor confirmed what Marshall and other military leaders already knew: they needed a secure system for communication with their troops, one that could not be cracked by enemy forces. They turned to a company called Bell Labs, which in the 1920s had developed the Vocoder, an early voice encoding machine which took analog recordings, capturing the sounds as they were naturally emitted. The Vocoder recorded people's voices and divided them by frequency into different pieces. It sent those pieces separately via radio waves to a machine on the other end, which received the different pieces and spliced them together to recreate the original sound.
Based on these sentences, what does "encoding" mean?
recording a message so that it is perfectly preserved and understandable
deleting a message so that no one can access it aside from the recipient
adjusting the volume of a message so that it can be heard more clearly
changing a message in some way so that it cannot be understood
Choose the answer that best completes the sentence.
The Vocoder was an analog voice encoding machine, ________ SIGSALY was a digital system.