I finally know what the Model 1 Ext port was actually used for.

It was used for Game switching on the Sega Ds-16 Store demo unit.

I remember these things, they were all over kmarts back in the day. they hold 6 cartridges and let you select one Very similar unit to the playchoice.

mvsfan wrote:

It was used for Game switching on the Sega Ds-16 Store demo unit.

I remember these things, they were all over kmarts back in the day. they hold 6 cartridges and let you select one Very similar unit to the playchoice.

My dentist still has one. Except it's wired into a model 2 it just uses the cartridge slot.