The use of SQUIDs enables the ultimate switching speeds and low power dissipation of Josephson devices to be achieved in digital logic systems. In addition, unique circuit capabilities become apparent which can simplify the logic circuits. These concepts will be applied to fast analog to digital conversion. A continuous signal is applied to a single‐junction SQUID and converted to a pulse train of flux quanta. These quanta are counted in a scalar consisting of a linear array of coupled DC SQUIDs. Scaling is achieved by utilizing the bistable nature of a double‐junction SQUID biased at the half‐flux point. In this way fast, single‐flux quantum logic can be achieved.