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Watching the Clocks

Setting VCR clocks automatically created a lot more problems than anyone realized

13 min read

In October, IEEE Spectrum reported on two problems confronting some U.S. users of videocassette recorders having automatically setting clocks ["Does anybody really know what time it is?," by Tekla S. Perry, October, pp. 26-28]. In some places they were seriously fast and in others seriously slow. The so-called autoclocks get their information from a digital time stamp sent by most Public Broadcasting System (PBS) stations during the television screen's vertical blanking interval. Sometimes called the XDS (extended data service) signal, for a time it was also being sent out by some Fox network affiliates. A VCR with an autoclock searches for the time signal, starting with the lowest-frequency channel in its vicinity and moving higher. Once it finds the signal, it stops searching

In San Jose, Calif., for example, some viewers were faced with clocks that were 24 minutes fast, because the time stamp being sent by a local PBS affiliate was incorrect. In other parts of the country, some viewers were faced with clocks one, two, or three hours slow, because some Fox affiliates were passing along time stamps set to the local time in Los Angeles. These errors were fixed last summer.

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The Device That Changed Everything

Transistors are civilization’s invisible infrastructure

2 min read
A triangle of material suspended above a base

This replica of the original point-contact transistor is on display outside IEEE Spectrum’s conference rooms.

Randi Klett

I was roaming around the IEEE Spectrum office a couple of months ago, looking at the display cases the IEEE History Center has installed in the corridor that runs along the conference rooms at 3 Park. They feature photos of illustrious engineers, plaques for IEEE milestones, and a handful of vintage electronics and memorabilia including an original Sony Walkman, an Edison Mazda lightbulb, and an RCA Radiotron vacuum tube. And, to my utter surprise and delight, a replica of the first point-contact transistor invented by John Bardeen, Walter Brittain, and William Shockley 75 years ago this month.

I dashed over to our photography director, Randi Klett, and startled her with my excitement, which, when she saw my discovery, she understood: We needed a picture of that replica, which she expertly shot and now accompanies this column.

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Paying Tribute to 1997 IEEE President Charles K. Alexander

The Life Fellow was a professor at Cleveland State University

4 min read
portrait of man smiling against a light background
The Alexander Family

Charles K. Alexander, 1997 IEEE president, died on 17 October at the age of 79.

The active volunteer held many high-level positions throughout the organization, including 1991–1992 IEEE Region 2 director. He was also the 1993 vice president of the IEEE United States Activities Board (now IEEE-USA).

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Get the Rohde & Schwarz EMI White Paper

Learn how to measure and reduce common mode electromagnetic interference (EMI) in electric drive installations

1 min read
Rohde & Schwarz

Nowadays, electric machines are often driven by power electronic converters. Even though the use of converters brings with it a variety of advantages, common mode (CM) signals are a frequent problem in many installations. Common mode voltages induced by the converter drive common mode currents damage the motor bearings over time and significantly reduce the lifetime of the drive.

Download this free whitepaper now!

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