Macintosh: S-Video Port Confused with the ADB Port

The mouse or keyboard on my new Macintosh computer does not work. I have tried different mice, different keyboards, and different ADB cables. I have tried starting up from my system software CD and startup floppy disk, and still get no response from either my keyboard or mouse. I know I am connected properly because the cable fits in the port.

What is wrong?
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Since you have tested for bad cables, mouse devices, keyboards, and software, make sure you are connected to the actual ADB port and not just a port into which the cable fits.

Many new Macintosh computers come with AV capabilities or installable AV options. The S-Video port on computers with AV capabilities has seven instead of four pins but an ADB cable will fit in this port. You may have attached your mouse or keyboard to this S-Video port. The icon next to the S-Video port is a box with an S in it or a Camera outline with an S in it.

Make sure the ADB cable is connected to the ADB port. The graphic next to the ADB port has a vertical line that connects with two dots to the left and one dot to the right:

If an AV video card is added to the following computers, the S-Video port could be mistaken for an ADB port:
Macintosh LC 580
Macintosh LC 630
Macintosh Quadra 630
Power Macintosh 5200/75 LC
Power Macintosh 5300/100 LC
Power Macintosh 6300/100 LC
Macintosh Performa 580
Macintosh Performa 630 series
Macintosh Performa 640CD DOS Compatible
Macintosh Performa 5200 series
Macintosh Performa 5300 series
Macintosh Performa 6100 series
Macintosh Performa 6200 series
Macintosh Performa 6300CD

The following computers have an S-Video port built-in:
Macintosh 660 AV
Macintosh 840 AV
Power Macintosh 6100 AV Series
Power Macintosh 7100 AV Series
Power Macintosh 8100 AV Series
Power Macintosh 7500
Power Macintosh 8500
Published Date: Feb 19, 2012