Some weeks ago, I stumbled upon this set at eBay. The Lego Dacta series was (and is) a kind of mysteris for me... good sets, but not available to the public. I guess, some of the would have sold well as regular retailer's items.

1039 is a supplemental set designed to work with 1980ies 4,5V/12V electric parts, simply everything before the 9V/electric system was introduced:
870 / 8700 Technic motor
107 Basic motor
970 Lighting bricks

We get 3 train remote control switches, but with special printing patters on them. You can combine them to a nice-looking control pane, and connect them to the 4,5V cell battery box or to the train 12V power supply.
Because the switch 4352 of set 8700 never really worked, this arrangement improves the situation. Now, you are able to control up to 3 motors or lighting circuit using a neat solution.
For obviuous reasons, it is recommended to use this arrangement only for non-mobile creations ;-)