• _{2 states, all possible combinations for a given number of digits}
• _dibit
  • _{00, 01, 10, 11}
• _tribit
  • _{000, 001, 010, 011, 100, 101, 110, 111}
• _quadbit
  • _{0000, 0001, 0010, 0011, 0100, 0101, 0110, 0111}
  • _{1000, 1001, 1010, 1011, 1100, 1101, 1110, 1111}
• _{quam (quadrature aplitude modulation)}
  • _{8 different phases and 2 different amplitudes}
• _{tcm (trellis coded modulation)}
  • adds a fifth bit to verify the quadbit