The Video [Input] card is very common, and is installed in the leftmost (from the rear) connector on the motherboard, and uses the leftmost upper knockout. It has NTSC Composite Video Input (yellow RCA) and Right and Left audio Input (Red and White RCA) jacks and an S-Video [input] jack.
The Apple External Video [Output] Connector is much less common. It has a very small circuit board with an attached ribbon cable that plugs into small connector in the middle of the motherbaord. It presents a Macintosh 15-pin two-row connector to connect to an Apple Display. Since it is intended for use with a display or projector, It has separate Red, Green, Blue, H-Sync, and V-Sync signals. Most TV sets require NTSC Composite Video or S-Video, which is not offered by this device.
The Apple External Video [Output] Connector can be used with any of the 520, 550, 575, 577, 578 series, and 630; in addition to the 5200/6200, 5300/6300, 5400/6400 and 5500/6500 and similar models with slide out motherboards.
This diagram (for the 6400 motherboard) shows the motherboard and connectors, labeled "Video In Card" and "Monitor Out Slot", respectively. The 6500 is strongly similar.
http://www.macgurus.com/products/motherboards/mbppc6400.php