Apple Power Macintosh (7100 Series) - Manual (Page 51)

The S-video connector is a round plug with several small metal pins. You can
plug this type of connector into your computer’s S-video input or output port.
IMPORTANT The S-video connector resembles other Macintosh connectors,
such as those for a printer, modem, mouse, or keyboard. Don’t confuse the
connectors; they’re not interchangeable.
Using adapters for composite video
Many video devices use composite video format instead of S-video. The
cables for these devices have RCA-type plugs.
RCA plug. Use the adapters that come
with your computer to plug this type of
connector into your computer’s S-video
input or output port.
S-video connector
41 Connecting Additional Equipment