Nuts & Volts - February 2006

READER FEEDBACK

EVERYTHING FOR ELECTRONICS

PATENT PROBLEM REVISITED

In your Reader Feedback, the short comment by T. Tofte called “Patent Problem” telling the history of the FET, a book called Designing With Field-Effect Transistors by Siliconix, Inc., revised by Ed Oxner, page 2 shows a partial reproduction of a patent Jan. 28, 1930 (1,745,175) by Julius Edgar Lilienfeld of Brooklyn, NY on an early Field Effect Transistor.

Ronald Robbins, El Cajon, CA

frame, we use 208 bits for field information and 96 bits ( 96 bit times) for the interframe gap, giving 304 bits. Let us call this the overhead. If we transmit nothing but 72-byte minimal-length Ethernet frames for an entire second, we will be able to clock out 14,880 complete frames using 10 Mbps Ethernet (100 nanoseconds per bit). Now imagine how many bits are involved when we multiply 14,880 frames by the overhead of 304 bits per frame. Specifically, we are talking about 4,523,520 bits. That is 45% of our 10,000,000 bit bandwidth. That leaves almost 5,500,000 bits for carrying data each second.

WRITER NOT RIGHT

Imagine my horror at discovering a series of math errors (all based on the original error) in my recent Let’s Get Technical column. Here are the corrections. So sorry ... I am usually quite picky about checking my work.

James Antonakos, Writer

Switching to units of bits, we have 26* 8 = 208 bits of field information in each frame. The way Ethernet is designed, there is always an idle time period after each transmitted frame. This is called the interframe gap, and it corresponds to 96 bits worth of time. So, when transmitting an Ethernet

NO END IN SIGHT?

It didn't register in November, but in reading the December issue and realizing that I was flipping pages backwards after each article — asking, is this really the end? — it struck home. That bright NV at the end of each article was really very helpful. Come on guys, if it ain't broke, don't fix it !!!

Dick Greet, Rye, CO

ON THE BRIGHTER SIDE ...

Never mind those soreheads ... In The Trenches has been one of my favorite columns, along with the tech answers and "Tech-newlogy." And as for the layout, while it may actually have slightly less print space, it's more readable (which I'm sure was the intent).

The only complaint I have is the pages makes photocopying harder — in the January '06 issue, I saved so much stuff, I just pulled the pages and rendered it almost worthless for passing on.

Eric Jones

by J. Shuman

Continued on page 31

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