# SDMB Monthly Photo Competition - rolling discussion thread **URL:** \ **Category:** Cafe Society\ **Tags:** photo\ **Created:** [November 27, 2022, 8:27pm UTC](https://boards.straightdope.com/t/sdmb-monthly-photo-competition-rolling-discussion-thread/975642 "2022-11-27T20:27:53Z")\ **Posts on this page:** 1\ **Showing post:** 1062
**Author:** ![Bob\_Blaylock](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_blaylock/32/3235_2.png) [@Bob\_Blaylock](https://boards.straightdope.com/u/Bob_Blaylock)\ **Post date:** [July 5, 2024, 7:56pm UTC](https://boards.straightdope.com/t/sdmb-monthly-photo-competition-rolling-discussion-thread/975642/1062 "2024-07-05T19:56:48Z")
  Many years ago, as a student of electronics, I happened to mention, while I was at my church, that I wanted to acquire an oscilloscope.  A lady nearby heard that, and offered to give me this one, which had belonged to her late husband. I think that was some time in the 1990s.   It’s a Tektronix 502A, possibly almost as old as I am. > [@Monthly Photo Competition #20 – July, 2024 – “Bridges”](https://boards.straightdope.com/t/monthly-photo-competition-20-july-2024-bridges/1003772/3): > >   A [bridge rectifier](https://en.wikipedia.org/wiki/Diode_bridge), made from four diodes, in front of an oscilloscope display showing what it does.  An alternating current (AC) signal is being fed into it via the black and white wires, and is displayed on the upper trace of the oscilloscope.  The ticked line on the oscilloscope grid, over the upper trace, indicates the zero-volt point.   The lower trace shows the direct current (DC) signal coming out of the bridge rectifier, via the red and green wires.  The line at the bottom of the wave… --- _[View the full topic](https://boards.straightdope.com/t/sdmb-monthly-photo-competition-rolling-discussion-thread/975642)._