Imac using composite tv cables

I have a visual system in my bar, which feeds out to 6 tv's all the insert plugs are standard composite cable (yellow plug) sockets.

Several times I have connected my MacBook to the system through the Apple Mini-DVI to Video Adapter.

I recently bought the new high definition iMac 21".

For some reason I connect the composite cable through the Mini DisplayPort to DVI Adapter through an added adapter or Mini DisplayPort to VGA Adapter through an added adapter.

The iMac doesn't know there is anything connected.

Can anyone help me???

You're not going to get to composite from the mini-display port with out using a digital to analog converter box.

Something similar to this. That is a typical price range.

As in the case with the one linked, no content using HDCP will display through S-video or composite on any of these devices being produced today.

Your other option is going to be getting an external USB video card or adapter that has S-video / composite output connections. These are getting extremely hard to find also.

Composite should have died 15 years ago. Those with TV's and projectors only having S-video and composite inputs are going to have a harder and harder time from here on in getting any current model device to work with them.