While a book block is nipped between a pair of clamping plates and passes through processing units in succession, perfect book bind processing is carried out. By measuring the resonant frequency of a given set of tags using a reader antenna and comparing the measured frequency to a reference resonant frequency, the observed frequency shift is used to ascertain certain properties of the set of tags, such as the number of tags present or the relative positions thereof. Total signal transmission time around the daisy chain bus structure as well as signal transmission time to each one of a plurality of client devices connected to a host device by the daisy chain bus structure may be readily determined. The control subsystem includes an RF transmitter configured to transmit a transponder activation signal, and an RF antenna network for relaying the transponder activation signal to a receiver of the portable unit to activate the transponder thereof. The regulating unit is coupled to the reference current source and outputs a current signal for adjusting a reference current of the reference current source.