Abstract: An apparatus and method according to the invention for determining respective deviations in the total number of signatures in each of a plurality of individual successive stacks from a given number of signatures having a ram for compressing the stacks of the signatures, a linear differential voltage transducer for measuring the relative heights of signature stacks by measuring distance that the ram travels, control apparatus comprised primarily of a programmable controller for processing the output of the transducer and optical detection means for monitoring the stack top for a sheet indicating that the stack has an odd count and disabling the control apparatus for indicating deviations in stack count. Additionally, a strapper which includes the apparatus for determining the count deviations adapted to monitor the position of a belt drive.