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National Company Advertisement: AC Power Strip
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Could this be the world's first publically documented rack-mounted AC power strip? The National Company of Cambridge, Massachusetts, which began life as the National Toy Company, ran a long series of advertisements in QST and other electronics magazines that were heavy on text and light on pictures - definitely not the norm in advertising. This one, number 62, from a 1939 issue describes, along with a reference frequency oscillator, how their engineering team fabricated what we now call an AC power strip for use in an equipment rack. According to the sketch provided, there does not appear to be an On/Off switch and almost certainly not any form of surge protection as is common (maybe even required by UL) for modern power strips. Someone at National should have patented the idea; their heirs would be rich today. National Advertisement Number sixty-two of a series
In the past, we have strongly recommended the HRO's equipped with 2.5 volt tubes over those equipped with 6.3 volt tubes where operation was to be from an AC power pack rather than batteries. This recommendation was based largely upon the difficulty experienced with modulation hum encountered in the vicinity of 15 mc. when AC was used on the 6.3 volt tube heaters. For some months now, the 6.3 volt tubes we have been receiving from both of our suppliers have been so completely free of this former trouble that we are now able to offer a 6.3 volt tube HRO for AC operation that in every way equals the 2.5 volt tube model. A new power unit, the No. 697 (same rating as the No. 5897 but with 6.3 volt, rather than 2.5 volt, heater supply) is also now available. This new power unit should not be used with the 6.3 volt HRO's heretofore supplied for battery operation, as the plate voltage will be much too high. Incidentally, all National power packs are now furnished complete with rectifier tubes, at no additional charge. James Millen
Posted June 3, 2022 Here are all the National Company advertisements I have:
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We have just completed a 100 kc. crystal oscillator
for our own use that we think is pretty nifty. It is designed for relay rack mounting,
is completely self-contained and has a front-of-panel control for the crystal holder
air-gap, so that the frequency can be checked and adjusted against WWV or any of
the "even 100 kc." broadcast stations by adjusting the proper harmonic for zero
beat. The oscillator tube is an 1851, and the rectifier a 6X5. Useful harmonics
for receiver calibration can be had as high as the 14 mc band. Thus when used in
connection with a good ham receiver the frequency measuring requirements of the
new FCC regulations can be complied with on the 160, 80, 40 and 20 meter bands.
Of course our "National" parts were used throughout except for the crystal, which
is one of Herb Hollister's. As this space is much too small to give further details
here, we have prepared a small descriptive pamphlet (with the hope, of course of
selling a few of our parts) which can be had from any of our regular franchised
dealers, or free by mail. 
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