"Activate all resolutions"
The "Monitors" control panel relies on the sense pins connected to the video output. In System 7 one has to open the control panel with depressed option key to permit the choice of any resolution the graphics card AND the monitor are capable of. On fixed frequency monitors nothing happens. For multsync monitors usually you will see some additional resolutions within the range of standard resolutions to choose from, like 640 x 480 at 60 Hz or 800 x 600 at 56 Hz. On a CRT monitor you would call those settings not ergonomic, what is why they are hidden. The option-enabled control panel still should do no harm to your monitor or leave you with a blank screen, however.
Opposite to the description above there is a control panel (or was it an extension?) available that permits to choose from any resolution/frequency the graphics card is capable of, no matter what monitor is identified be the sense pins in the connector. The "Activate all Resolutions" software has no user interface, settings are to be made through the "Monitors" control panel. This will allow to use settings the connected monitor might not work with. For example you could set the output with a connected Apple 13" to 1024 x 768 pixel at 75 Hz, but it will not produce a readable picture on the screen (and hopefully will not damage the screen, but I recommend not to try so!).
Now, what is the use of this "Activate all resolutions" thing? You need this when you use a Mac-VGA adapter to spoof sense pins (the VGA monitor connector does not support sense pins, nor does it physically fit to the Mac monitor connector). In case you use a PowerBook, you might want to carry only one adapter to connect external monitors to your computer (like a video projector). An adaptor with switches to change sense pins provides no extra reliability, as you need to double check the settings with the monitor specifications, anyway. So you could make a simple adaptor, providing a basic sense pin setting like 640 x 480 at 66.7 Hz, which will not damage most monitors when used in the hands of someone who does not know about Mac monitor specifics. One might also add one switch to change to sync on green (like in some switchable adaptors). With this adapter and the possibility to soft-set the output resolution you will successfully connect any external monitor within the range of the graphics card.
You even can have a use for a Mac-VGA monitor adapter with no external monitor present at all. In case you have a Mac with a monochrome or greyscale display and with a second graphics card capable of colour output, you can plug in just the monitor adaptor, set to simulate a coulour display. Because of the sense pins in the adaptor the Mac "thinks" there is a coulour display hooked to the output. Now open the "Monitors" control panel, set the output mode to "mirroring" (firstly!) and set the non existent colour monitor to be the main screen (with the menu bar). Now you can use applications that require colour output w/o having a colour display. Once I used this for some games on a PowerBook 180
It might work well for something like a SE/30 with a colour server card.
