Monday, July 30, 2012

Facebook's Illusion of Privacy

...whatever you post on Facebook, you should just assume that the public can see it, because even though Facebook tries to put in protections and permissions and privacy controls, there’s really no way to guarantee that only your friends can see your data.

Tuesday, July 17, 2012

Putting Water Adhesion and Cohesion to Work

I lost the grommet that allows me to attach a drain hose to my air conditioner.  So I decided to see whether water's properties of adhesion and cohesion would come to my rescue.

I suspended the drain hose below the air condition drain opening.  Then I placed one end of a wet, rolled up paper towel in the air conditioner, touching the drain pan.  I placed the other end into the hose.  The set up is shown below.

Normally, you'd just let the water drip out onto the ground.  But this A/C is installed between a kitchen and a carpeted enclosed porch, and we wanted to keep the carpet dry.

The rig works like a charm.  No spillage.  All the condensate ends up in the bottle, which I then empty into the washing machine or the garden.  In fact it works better than if I'd used a grommet to connect the hose.  With the grommet, the water level had to rise high enough to breach the rim of the grommet.  In fact, I used to put a piece of cotton string in the grommet to help lift the water up over the grommet ledge and into the hose.  Otherwise, the water would leak out all four corners of the pan.

There is some rust forming around the edge of that unfinished knockout.  I'll need to paint that at the end of the season if I don't want the rust to spread.

Friday, July 13, 2012

How I Became Paging System Monitor

One of my unofficial volunteer work responsibilities is that of Paging System Monitor.  This is someone who listens to a page over the public address system and then verifies that the pager hung up properly.  Because if the person does not hang up the phone, no one else can issue a page.

Generally this doesn't happen often.  But when it does, it's inconvenient.  It can be embarrassing, too, if the pager continues speaking, thinking that the conversation is not getting broadcast to all the bosses.

Usually it's an easy job to find the off-hook phone, if the person included the (correct) phone extension number in the page.  When you hear, "Joe Smith please call 73," for example, you can assume that the pager used the phone at extension 73.  Then if the phone was not hung up properly, you (or Joe) can just call it, and that phone should ring on the second line.

But if it's one of those generic announcements, such as, "It's starting to rain.  If you left your car windows open, now's a good time to close them;" or "I'll be rebooting the file server in five minutes.  Please close all open files;" or "Would the janitor please come to the men's room -- it's an emergency.  Please bring a mop," then the process turns into a fun game of deduction.

Well, in the case of the call for the janitor, you can assume that the phone is near one of the men's rooms."  So you can walk over to any nearby office and check the phones.  But if a location isn't implied, then you have to revert to recognizing the sound of the voice and then figure out whom it belongs to.  This is easier than you might think.  In fact, I had a good lesson in grade school in how easy "voice recognition" really is.

We were reading a story out loud, and the plot hinged on a character figuring out who someone was just by the sound of his voice.  I asked the teacher how that could happen, and I expressed doubt that you can know who was speaking to you without actually seeing the person.  So the teacher decided to really convince me.  She invited me to close my eyes.  Then one by one, each of my classmates spoke, and I had to guess who it was.  There were only two out of about 30 voices that I couldn't figure out (and one of them belonged to someone named Joe, in fact).  Yes, the teacher was pretty cool.  But it was Open House Day, and our parents were also in the room.  So I suspect she might not have done this if she weren't showing off for them.

Anyway, once you know who the person is, you can usually resolve the problem by calling his or her extension.  Or you might have to walk around and find the person and then ask which phone was used.  I had to do this recently for an announcement the janitor made about locking up the building.  Usually he locks the building because he's the last to leave.  But since he was leaving earlier than usual, he wanted to let us know that one of us had to lock up.  It's a good thing I found him because he used a phone deep in purchasing that I wouldn't have guessed right away.

All this rigamarole wouldn't be necessary if the phone system's PA mode were designed to "time-out" after 30 seconds.  But again, technology fails us yet again, and we resort to wasteful effort to compensate.

Monday, July 02, 2012


I bought the GPS about one month before driving my family to Washington DC.  In order to get used to it, I would use it on my work commute.  I quickly discovered that it had an undesirable habit of choosing congested roads with many traffic lights.

It didn't seem to matter whether I choose Shortest Route, or Quickest Route.  It was oblivious to the Avoid Highways setting.  Even the intriguing Econo-Route setting made no difference.  It was stuck on an undocumented mode I call "Maximize Encounters with Red Traffic Lights."  And where I drive, at least every 1 of 4 traffic lights will be red on any given commute.  If you know how many traffic lights (L) are on the route, you can get a realistic arrival time (if you obey the speed limit) by adding this many minutes to the arrival time the GPS claims: T = 0.5 * L.  My meager 10-mile commute to work features an amazing 21 traffic lights and is ten minutes shorter at 3am when most lights are either green or disabled.

And unlike Monty Python's Flying Circus, I hate traffic lights, even when they're green.  Because a green light is one that is bound to turn red just as you get to it.  Of course anyone who has read my rant on traffic lights (and the follow up post) knows where I stand.