This article is about the digit magazine pdf february 2017 of information. This usage distinguishes the quantity of information from the form of the state variables used to represent it. When the logical values are not equally probable or when a signal is not conveyed perfectly through a communication system, a binary digit in the representation of the information will convey less than one bit of information. However, the shannon unit terminology is uncommon in practice.
Bell Labs memo on 9 January 1947 in which he contracted “binary information digit” to simply “bit”. Bits can be implemented in several forms. The specific voltages are different for different logic families and variations are permitted to allow for component aging and noise immunity. 0 and 1 at the output of a device are represented by no higher than 0. 4 volts and no lower than 2.