Rapid Fire Unit

From Sonic Retro

The Rapid Fire Unit is a small device that is inserted between a two-button controller and the Sega Master System. It provides an auto-repeat capability for the control buttons which saves a lot of wear-and-tear on fingers for games like Astro-Warrior. The auto-repeat could be turned on for each button independently.

     Switches to turn on/         
     |     off auto-repeat         
       Plug for           V                               
 system     -----------------         
   |        |               |         
   V        |      2 [X ]   |         
  ---       |               |        
  | |=======|  RAPID FIRE   [<- Plug for         
  ---       |               |  controller         
            |      1 [ X]   |         
            |               |         
            -----------------         
    
  ASCII art by Brett Carver         

This unit was seen offered through Sega in their early "SEGA Challenge" newsletters. Buying 3 games would get you the item. It was also available via retail ($8.50), and packaged with the Control Stick as the "Rapid Fire Control Stick" ($??.??). A 3rd party rapid fire unit may exist.