The UnimacFly was the ultimate configurable monitor adapter for connect various sizes and types of VGA monitors to a Macintosh with the Apple DB-15 monitor port. The proprietary Apple monitor port was introduced on the Macintosh IIci range in 1989 and was used on Apple desktops up until the switch to industry standard VGA ports in 1999. Three of the 15 pins were 'sense pins' and the host Macintosh poled these pins to identify the type of monitor attached. Diodes were used in different combinations between these pins to communicate the monitor resolution and frequency.
The UnimacFly adapter features eight switches under a hinged door which when set according to the settings shown in the table on the adapter, tell the Macintosh which resolution and type of monitor is connected.