==== Nexa ====

  * Mark length encoding.
  * Seems to use every other bit only
  * Seems to start with a start bit = 0
  * Group signalling uses shorter spaces between bits in the middle


  * One buffer with -100 and one buffer with 100, just choose length
  * A Message class and a message sender which reads pulselengths from the message
  * Use two transistors, a NPN followed by a PNP
  * use the board of the sender!