Be liberal in what you accept, and conservative in what you send.

—Postel's Prescription, by Jon Postel

I have a day job as a hardware engineer for a telecommunications company, and in this capacity I'm often designing equipment to be installed in phone company Central Offices (COs). Unlike the designers of consumer electronics or data center hardware, I can rely on having DC available to power my devices; COs have “rectifier plants” that convert mains AC to 48-volt DC and distribute this power through the facility with giant copper or aluminum busbars over the racks.

Most CO equipment uses two-pin Phoenix-style connectors as power inlets. These come with a pluggable terminal block with screw-down style connectors that accept bare wire from the rack's fuse and power distribution panel. Because installers wire this plug on site and mistakes are easy to make, it's good sense (and company policy) for the hardware designer to put a bridge rectifier across the input leads so that this connection can be insensitive to polarity.

This is an application of the first part of Postel's Prescription, “be liberal in what you accept”, to power engineering. If the second part, “conservative in what you send”, has an analogue in this field, it could be this: make sure your power outputs, if any, have clearly defined polarity. Another possible analogue would be: keep the output to a tighter voltage range than the telecom standard 36-72 volts.

None of us can fully escape this blindness, but we shall certainly increase it, and weaken our guard against it, if we read only modern books. Where they are true they will give us truths which we half knew already. Where they are false they will aggravate the error with which we are already dangerously ill. The only palliative is to keep the clean sea breeze of the centuries blowing through our minds, and this can be done only by reading old books. Not, of course, that there is any magic about the past. People were no cleverer then than they are now; they made as many mistakes as we. But not the same mistakes.

—C. S. Lewis, from his introduction to Athanasius' On the Incarnation *

I like this idea that old books can be an antidote to the unexamined pieties of contemporary thought, and have been putting Lewis' suggestion into practice; at the moment my daily reading is split almost equally between a just-released and currently-best-selling work of pop psychology and Edward Gibbon's The Decline and Fall of the Roman Empire (although I suspect Lewis would not have counted this as “old”, preferring to read the actual Romans themselves, Gibbon is revered enough and indeed, old enough to have entered the canon himself, even if through the side door).

This is an older drawing of a hut from somewhere in Southeast Asia, after a photograph in Architectural Digest. I drew this with a black Pilot G2 05 pen in the sketchbook I was using at that time.

I've redesigned my personal site and blog, and would appreciate criticisms or comments. The layout adapts to a wide variety of screen widths using CSS media queries; try scaling your browser window or looking at the site on your mobile phone to see what I mean.

As a way of trying out github for myself I uploaded a small script that iteratively solves the Colebrook equation for the Darcy-Weisbach friction factor, which can be used to estimate head loss due to pipe friction; this played a very minor role in my recent MSEE thesis. The script runs in GNU Octave and it certainly should run in Matlab as well, although I haven't tested that.