Great answers.  I have but one thing to add:

On 2/16/2016 10:36 AM, Bruce  Johnson wrote:

> Well, make ‘em work for it…they have to macguyver a long range sensor from some aluminum tent poles, a walkie-talkie, and some window screen :-)

There should probably be a children's educational toy in there
somewhere, too.

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Kelly St. Clair
xxxxxx@efn.org