The history and background to these toys has been documented and explored much better than I can do here by fellow collector Joe Lang at his own website. Go take a look at the complete line there. Meanwhile, ill give you a brief taster here showing the modular Base Station and vehicles.
During the eighties, I was a complet Star Wars obsessive and nothing else would do, so although I did see the toys on the shelves, I overlooked them for the much more gawdy creations of Kenner. I have managed to piece together an almost complete set of the vehicles and part of a base and just today, thanks the the generous and considerate Mr Lang, I have added the rarest of the rare. Tandy picked up the basic design of the toy and expanded the concept still further with this Mars Mission Explorer - this has tracks in place of the toothed wheels and comes in a wonderful shade of deep space purple!
Finally, Ive added in a picture of some distant cousins - the fixer-upper on the top left is a Power Climber toy and sits next to an orange Tomy Adventure Buggy. Front line is a mystery Moon Bus courtesy of Mr Woods car boot foraging and lastly a 6x6 Amphibian Truck, as at home on water as on land. Ive added in an Explorer 12 Polar crewman for scale.