The quibinary code is a 7-bit code whose 7 bits always contain only two "ones". So there are never more than two bits set to "1".
In terms of structure, the first bit shifts forward one bit position for every second digit, while the second bit is always represented by a Least Significant Bit( LSB) or by the bit preceding it. The quibinary code is redundant and error- proof. However, it is hardly ever used because its 7 bits do not fit into the byte scheme(8 bits).