Are the transmissions from the keypads to the receiver encrypted?

The voting data when transmitted by a keypad to the receiver is not encrypted, however it is obfuscated using a custom protocol with a format that is not published.  It does not use standard radio protocols such as Bluetooth, WiFi or Zigbee.

In addition there is no context sent with the vote, the only data that is transmitted is the value of the button pressed, e.g. 0, 1, 2, 3, 4, etc.  The keypad number that is sending the vote is not transmitted over the radio.  The USB receiver interprets the keypad number based on the timeslot allocated when the system was setup and the keypad numbers programmed, only the receiver is able to do this to marry up the vote received with the keypad number that sent it.