Need help with Import console

I recently acquired a japanese Dreamcast, as well as what is supposed to be a US unit(as a spare)(I have a working US unit I've been using.).
When attempting to use them, I found to odd things:

1) the AV cable has S video connection instead of a yellow cable head.
2) both units have a flat connection point into the Dreamcast instead of having a room for the notch on the bottom(of the connector) that my other unit's cable has.

Did the Dreamcasts change over to S video at some point or that something typically only seen on imports?
Unfortunately the tv I use doesn't have S video capability. Is the other type of AV cable offered for this version or do I simply have to have S video capability to use these units.
Any help on this matter would be greatly appreciated.

All dreamcasts as far as I know can do composite or svhs (and even vga on games supporting it).
So you just need another A/V cable, or you can use an svhs to composite adapter, this shouldn't be very expensive.

S-Video is made up of RGB channels, same as Scart, all Dreamcast's output this.

The hardware is the same (A/V pinouts will be the same). The only differance is the cable. As semicolo suggested just buy a composite A/V cable, it will work perfectly.

S-video doesn't use RGB, just luma and chroma if its done right, and if its done cheesy (like a composite to s-video adapter), just a single composite wire.

Yes svhs and rgb are totally different, svhs is close to composite.
in composite chroma and luma are mixed together.

Are you sure that a svhs input will work with a composite input toodles (do you mean composite sent to chroma or luma with the other grounded ? Or even sent to both ? anyway I don't see how the video could be decoded correctly)

Ah, i see, being from the UK i never use s-video, i always wondered what luma and chroma were for on the DC A/V pinout.

i'm getting alot of stuff wrong lately, and giving bad advice, maybe i should research stuff more thoroughly instead of trying to do it off the top of my head.

All game systems outputs 480i. It is 640x480 pixels, interlaced.

Simple RF cables are the worst quality, with all signals going through the same "pipe".

Composit cables (red/white/yellow "rca") split the audio into two seperate cable (left and right) and the video into its own cable (yellow). Sound is greatly improved, video is improved as well, but not perfect.

S-Video divides the video information into two separate signals: one for color (chrominance), and the other for brightness (luminance). The audio is the typical red/white stereo cable.

Component uses 3 cables for the video. Red/Green/Blue. The Green cable contains brightness (luminance). The Blue and Red cables contain the color (chrominance) information. Its taking S-Video another step further.

These are the american standards for producing 480i.

The last you mention is Y/Cr/Cb, I don't think the dreamcast can output this, but it's composite and svhs related you're right.
In rgb mode, dreamcast really outputs red green and blue levels with horizontal/vertical syncs which is rather different.

Correct, the Dreamcast does not output any sort of component signal at all.