From Morse Code to Gigabit Ethernet

1. From Morse Code to Gigabit Ethernet Lisa Marvel US Army Research Laboratory Information presented here is, for the most part, based on C. Boncelet, “THE INVENTION OF THE TELEGRAPH MARKS THE BEGINNING OF ELECTRICAL ENGINEERING,” July 2011.

2. Outline • Some interesting history • Computer communication today • Morse Code activity • Video clip

3. History: 200 years ago • 200 years ago is not so long ago • Scientist just beginning to experiment with electricity • How was communication performed 200 years ago?

4. News traveled slowly … • War of 1812 • Battle of New Orleans January 8, 1815 • But peace treaty signed on December 24 1814 • ?? • Elections • Held in November • Inauguration in March

5. 1837: Communications speed up • Samuel Morse invents the telegraph • The switch and sounder could be located at separate locations limited mostly by the length of wire available • Information could be carried by a changing electrical current

6. Electrical Communication • Changing electrical current • Signals of high/low voltage/current • Represent 1s and 0s for communication and computation • This was a BIG (read HUGE) deal!

7. Electrical Infrastructure • Soon after the telegraph invention, wires were strung everywhere! • Messages could be sent “instantly” over long distances • Telegraph first electrical device to come into widespread use • Can you name the US telegraph company? What do they do today?

8. “Wire” Transfers • Western Union Offices • Send $ from person in one town to another • Send $100 to Aunt Doris … • $ do not move but the $ pass over the “wire” • Telegraph invention led to the invention of the interstate banking system

9. Telephone • 1876 Alexander Graham Bell invents the telephone • Similar to telegraph • switch -> microphone • Sounder -> loudspeaker • Transmits continuous signals vs. 1s 0s • Western union thought telephone a toy

10. Radio Communications • 1890s • Ships were equipped with radios using Morse Code • 1912 Titanic; survivors can thank radios • 1920 Broadcast popular • 1930s B/W Television • 1950s Color Television

11. Originally Computers were … • Human • Women Mathematicians -> “computers” • Calculated firing tables • ENIAC – 1946 • Sponsored by ARL predecessor, BRL • Was located @ APG

12. Some of these women were the first computer programmers! See DVD “Top-Secret Rosies: The female Computers of World War II”

13. Today … • Personal Computers, commonplace by 1980s • Cell phones (2-way radios), 1980s • Smart phone = radio + computer • It is not uncommon for a single person to own/carry several computers • What other important technology did we fail to mention?

14. Computer Networks • There are fewer unconnected (stand alone) computers today • Many applications require an internet connection • Now people may have multiple devices that connect to the internet: • Laptop • Desktop • Iphone/Blackberry • Kindle • Ipad/Other tablets • Streaming Video devices (e.g. Roku) • VoIP (magicjack, comcast voice, etc.)

15. ARPANET • Early computer networks • Government, government contractors and and Academia • No commercial function • BBN, August 1962, “Intergalactic Computer Network • ARPA RFQ, 1968 • 4 Nodes, 1969

16. http://en.wikipedia.org/wiki/File:Arpanet_logical_map,_march_1977.pnghttp://en.wikipedia.org/wiki/File:Arpanet_logical_map,_march_1977.png

17. ARPANet/MILnet topology circa 1983 BRL (Aberdeen) is the predecessor to ARL

18. How fast are computers • Measured in instructions/second • Typical laptop 2.6 Giga-instruction/second • Compare to communication speed Light can travel 3*108(m/s)/109(instructions/sec) = 0.3 (m/instruction) ~1 ft/instruction Electrical signal moves 1/3 ft/instruction • If we want fast computers, what must we do?

19. Speed • Electrical signal travel 2/3e • Electrical signal circles the earth 4-5 times/second • Light circles the earth in 7 times/second

20. Smaller/faster computers • Issues • HEAT! • Fast computer are liquid cooled (function similar to a radiator)

21. Next Saturday – www turns 20! On August 6, 1991, Tim Berners-Lee posted a short summary of the World Wide Web project on the alt.hypertext newsgroup. This date also marked the debut of the Web as a publicly available service on the Internet. 

22. Let’s talk about human Morse Code speed … http://rogerwendell.com/images/morsecode/morsecode_1939_newspaper.jpg

23. Transmission Rate • 75 words/minutes • If each word is 5 letters • A letter can be represented as a byte (8 bits) used ASCII code • So McElroy was transmitting at 75 * 5 * 8 = 1875 bits/minute or 31.25 bits per second

24. Internet connection bandwidths McElroy = 31.25 bits/s [edit] This table shows the maximum bandwidth (the physical layer net bitrate) of common Internet access technologies. http://en.wikipedia.org/wiki/Bandwidth_(computing)

25. Home internet speed; • Netflix, for HD content is about 4 to 8 Mbps

26. Activity • Build a version of a telegraph • Why a light bulb instead of buzzer? Light Bulb

27. Morse Code • Dot: Short mark “.” dot is one unit of time • Dash: “-” longer mark 3 times as long as “.” • Space between symbols is same length as “.” • Space between letters is same length as dash • Space between words equals 7 dots

28. Transmit a Message: Isolated Receivers • Group in teams of 4; Pick on person to be the sender : • No talking • Each receiver covers their paper and doesn’t share results • Advice: • Senders make a mistake just continue (sender in DC; receivers in Baltimore) • Receivers write down the dots and dashes and use a vertical line to mark spaces. Decode after msg sent.

29. Transmit a Message: Collaborating Receivers • Group in teams of 4; Pick on person to be the sender : • Talking among receivers aloud • Receiver can share results • Advice: • Senders make a mistake just continue (sender in DC; receivers in Baltimore) • Receivers write down the dots and dashes and use a vertical line to mark spaces. Decode after msg sent. • Try timing sender, how do they compare with McElroy?

30. What about Errors • Did you all receive the same message in the lab? • What if you receive the message 2 times? • Or 3? • Do you think you would reduce your number of errors? • Repeating the message is an example of a redundancy code

31. Morse Code on Leno