The Switch

The Topre Switch

What makes Topre Realforce keyboards special are the electrostatic capacitive switches. The ‘mechanical’ term is not quite applicable to a Topre switch, since it uses a mat of rubber domes and no metal contacts are used. The Topre switch is a little more complicated compared to the garden variety MX switch that we know and love.
 

 
Topre designed their switches a little differently, ‘the good feeling with the oneness of cup rubber’, it’s basically a slider over a rubber dome over a conical spring over a capacitive sensing mechanism on the PCB. If you followed all that, congratulations to you! In Topre’s world, most of the key feel, or tactility, is generated by the rubber dome sheet and the spring is there just for the capacitive sensing.

The capacitive sensing circuit of a Topre switch is generally thought of as a mechanical switch, even though no two pieces of metal meet to make electrons flow. Instead, a capacitive sensing circuit detects and registers a keypress when the capacitance reaches a given value. Capacitive sensing has several advantages over conventional switches, it eliminates contact bounce and chatter (the repeated letter phenomenon), which are usually filtered out by the controller. Capacitance sensing also are inherently capable of n-key rollover without the need for diodes. That’s neat. Since there’s no metal contacts to fatigue, the Topre switch is good for at least 50 million keypresses before they wear out.

Keypresses are registered midway down the stroke, like a typical mechanical switch. This also leads to the unique feature of the RGB, the APC, or Actuation Point Changer. More on that below.